June 16, 2025 • 30 mins
⚕️ FREE MSRA PODCAST – Scabies
🎧 A clear, high-yield breakdown of this intensely itchy parasitic skin infestation – perfect for exam prep and real-life clinical scenarios.
🧠 Key Learning Points
📌 Definition
• Scabies is a contagious skin infestation caused by the mite Sarcoptes scabiei var. hominis that burrows into the epidermis, triggering an allergic hypersensitivity reaction.
📌 Causes & Risk Factors
• Prolonged skin-to-skin contact
• Institutional living (e.g. nursing homes, prisons)
• Poverty, overcrowding, malnutrition, immunosuppression
• Sexual contact
💡 Mnemonic: “Close, Crowded, Compromised” for common risk factors
📌 Pathophysiology
• Female mite burrows into stratum corneum, lays eggs
• Mite products (eggs, saliva, faeces) provoke delayed-type hypersensitivity reaction
• In crusted scabies, mite load can reach millions, leading to extreme symptoms and infectivity
📌 Symptoms
• Severe pruritus, worse at night
• Widespread erythematous papules, vesicles or pustules
• Burrows: wavy, silvery lines in finger webs, wrists, genitalia
• Scabies nodules: chronic allergic lumps
💡 Mnemonic: “ITCH”: Intense, Typical sites, Crusted variant, Hypersensitivity
📌 Differential Diagnosis
• Eczema (atopic/contact)
• Insect bites
• Tinea corporis
• Psoriasis
• Lichen planus
• Impetigo (secondary infection)
📌 Diagnosis
• Clinical diagnosis via distribution, itching history, visible burrows
• Microscopy of skin scraping: mites, eggs, or faeces
• Dermatoscopy: Delta wing sign (mite at end of burrow)
• Ink burrow test
• IACS Criteria (Confirmed, Clinical, Suspected)
📌 Management
• Treat all close contacts simultaneously
• Permethrin 5% cream: first-line, whole body application
• Malathion 0.5% liquid: second-line
• Oral ivermectin for crusted scabies
• Repeat treatment after 7–10 days
• Hygiene: Wash clothes/bedding >50°C, seal non-washables for 72h
• Antihistamines, topical steroids for itch relief
• STI screening and public health notification if outbreak
📌 Complications
• Secondary bacterial infection: impetigo, cellulitis, sepsis
• Crusted scabies: high mite burden, resistant to treatment
• Psychological distress: insomnia, stigma
• Persistent itch and nodules after eradication
📌 Prognosis
• Excellent with correct diagnosis and treatment
• Delayed or incorrect treatment → reinfection, complications
• Crusted scabies: poorer prognosis, needs specialist input
📎 More MSRA Resources for Scabies
📝 Revision Notes: https://www.passthemsra.com/topic/scabies-revision-notes/
🧠 Flashcards: https://www.passthemsra.com/topic/scabies-flashcards/
💬 Accordion Q&A Notes: https://www.passthemsra.com/topic/scabies-accordion-qa-n
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Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
(00:00):
OK, picture this. You're hitting the books late,
trying to cram, but your skin isjust crawling.
The itching is relentless. It's driving you absolutely mad,
especially when you're warm or trying to sleep at night.
It's not just irritating, it feels like something's actually
under your skin. What could possibly be causing
(00:21):
this intense torment? Yeah, that sounds like a really
classic presentation of scabies.It's one of those conditions
that's, well more common than you might think.
Yeah, just incredibly uncomfortable for the person
going through it. And that's exactly what we're
unpacking today. Welcome to this deep dive
focused entirely on scabies. Our mission is specifically
tailored for you. If you're revising for exams,
(00:43):
you know like the MSRA, we want to give you a high yield focused
overview straight from the source material.
Exactly. We're going to slice through the
details to give you the essential knowledge what scabies
actually is, where it comes from, who's most vulnerable,
what it looks and feels like right, how you figure out if
someone has it in practise and crucially, how to effectively
treat it and, you know, stop it coming back.
(01:04):
Think of this as distilling all that key information into a
concise session designed to really stick in your mind.
Let's jump right in. So at its heart, what exactly is
scabies? OK, at its core, scabies is a
skin infestation. It's caused by a tiny little
parasitic creature, the Sarcopti's Scabiomite, and it's
highly contagious. So a mite is causing the problem
(01:27):
and the main symptoms people complain about.
Well, the defining features you'll see and hear about are
that intense itching, the puritus you just described, and
a characteristic rash. Now here's a really important
point, a key takeaway for revision the intense itching and
the rash. They are primarily caused by the
mite. Just like crawling around.
(01:47):
They're actually your body's allergic or hypersensitivity
reaction to the mites themselves, their eggs and their
waste products. Their faeces burned in the skin.
OK, so it's not the physical sensation of the mites so much
as your immune system reacting to these tiny invaders and,
well, what they leave behind. Spot on.
That immune response is what drives the intense inflammation
(02:08):
in that awful itch. And you know, while we might
associate it with certain stereotypes, scabies can affect
anyone, anywhere. It spreads primarily through
close, direct skin to skin contact, right?
The female mite needs to Burrow into the top layer of your skin,
the epidermis, to lay her eggs. OK, so it's an infestation
(02:29):
causing an allergic reaction spreading via close contact.
Let's get a bit more specific about the cause and how it
works. The aetiology.
What species are we talking about here?
Yeah, it's caused specifically by the Sarcoptis KBMI variety
hominis. This one's adapted specifically
to humans and the female might she's the the engineer here.
She tunnels into the stratum corneum that's at the very top
(02:50):
layer of your epidermis, creating those characteristic
Burrows. And she's doing more than just
tunnelling while she's in there.Oh.
Absolutely. As she tunnels along, she lays
eggs along the Burrow. Those eggs take about 10 to 15
days to mature. Once they hatch, the new mites
emerge onto the skin surface, They mature, they mate, and the
whole cycle just continues. An adult mite lives for about
(03:12):
four to six weeks. That's quite a life cycle
happening right under the skin surface.
How much contact is actually needed for transmission?
Is it just like a brief touch? Well, for typical scabies
transmission usually requires prolonged direct skin to skin
contact. The sources suggest this is
generally around 10 to 15 minutes of sustained contact.
(03:33):
OK. However, there's a really
important exception, especially clinically crested scabies.
Ah, the really severe form we hear about.
Precisely, in crested scabies, individuals have a
hyperinfestation. We're talking thousands, maybe
even millions of mites. Because of this incredibly high
might load, transmission is much, much easier.
(03:53):
It can occur via contaminated items like bedding, clothing or
furniture, which is pretty uncommon in typical scabies.
And there's a crucial point about the timing of symptoms
that's so vital for history taking, isn't there?
The itching doesn't just appear overnight after you've been
exposed. This is a super high yield
detail for exams and well for practise to the intense itching
(04:14):
that Puritus. It typically has a significant
delay, usually starts about fourto six weeks after the initial
infestation. Four to six weeks.
Why such a long delay? Well, because that's roughly how
long it takes for your body to develop the allergic
sensitization to the mites and all their products.
The immune system has to learn to react.
So someone could actually be infested, potentially spreading
(04:37):
mites around for over a month before they even develop the
main symptom that brings them toa doctor.
Exactly. And asymptomatic transmission is
also possible, which just adds another layer of complexity to
controlling outbreaks, doesn't it?
Yeah, definitely. It really highlights the need
for a high index of suspicion, especially in potential exposure
settings. That delayed reaction is
absolutely key to understanding its spread.
(04:59):
So who is most likely to get it?What are the major risk factors
we should be aware of? OK, several factors increase
susceptibility. Crowded living conditions are a
primary one, obviously, as they increase the likelihood of that
prolonged skin to skin contact needed for transmission.
Makes sense? Frequent physical contact with
infested individuals is, well, obviously a direct risk, and
(05:20):
while it's not the sole Causeway, poor hygiene can
sometimes contribute, maybe in the sense of delayed recognition
or perhaps a more severe resentation.
But it's really crucial to remember scabies can affect
anyone, regardless of how clean they are.
And certain locations just seem like perfect breeding grounds
for outbreaks, don't they? Absolutely, institutional
settings are the classic examples.
(05:42):
Nursing homes, prisons, childcare facilities, basically
anywhere people live or spend extended periods in close
proximity. Right.
Socio economic factors are also strongly linked.
Things like poverty, living in refugee camps, malnutrition and
homelessness are all significantrisk factors.
Dementia is listed as well, I noticed.
Yes, that's likely due to factors like reduced self-care
(06:05):
capacity or maybe difficulty communicating symptoms early on.
Sexual contact is another well documented route of
transmission. OK.
And certain populations are particularly vulnerable
children, especially in developing countries where
prevalence can be very high and critically immunodeficient or
immunosuppressed individuals. Like patients with HIV or those
(06:27):
on immunosuppressant therapy? Exactly those groups, their
compromised immune response can lead to much, much more severe
infestations like that crusted scabies we mentioned.
All these risk factors together explain why outbreaks can spread
so rapidly and vulnerable or overcrowded communities.
So we know what the mite is and how it gets around.
How does it actually cause the problems we see and feel?
(06:49):
Let's dive into the pathophysiology a bit, OK?
It all starts with that female mite burrowing into the upper
layers of the skin, the epidermis.
She then lays her eggs along thetunnel she creates as she goes.
And this is where the body's reaction really kicks in.
Precisely. The mites, saliva, the eggs she
lays and the faecal pellets the sabala left in the Burrow act as
(07:10):
foreign antigens. Your immune system recognises
these and mounts what's called the delayed type
hypersensitivity reaction. OK.
This is essentially an allergic inflammatory response happening
within the skin itself. So the intense itching and that
rash we see are basically manifestations of that localised
allergic inflammation. That's the key mechanism, yeah.
(07:32):
It's your body sort of overreacting to the presence of
the mites and their waste products just under the skin
surface. And as the eggs hatch, new mites
mature, create new Burrows, deposit more antigens.
This. Cycle just keeps going.
Exactly. The cycle of infestation and
allergic response continues, which is why the symptoms
persist and often get worse if it's not.
Treated. That makes perfect sense.
Your body is constantly fightingthese tiny invaders and their
(07:55):
leftovers, as you put it. Now that description, an icky
rash could fit a whole lot of conditions.
What else should be on our radarwhen we're thinking about
scabies? The differential diagnosis.
Yeah, this is a really critical area for diagnosis and for
exams, too. Scabies can be a great mimicker.
You definitely need to consider common itchy rashes like insect
(08:15):
bites. You know, various forms of
eczema, atopic contact dermatitis.
The usual suspects. Right, and fungal skin
infections like teeny corpus. Also don't forget secondary
issues that arise from all the scratching like impedigo or
other bacterial skin infections.Other possibilities on your
differential might include conditions like like blandness
or psoriasis, although their appearance is often quite
(08:38):
distinct if you look closely. Less commonly, perhaps in
widespread or atypical cases, one might even consider things
like bullispimphegoid or certainsystemic conditions causing a
rash, but they usually have other prominent features.
So a broad list. Yeah, the core task is always
differentiating it from the morecommon causes of widespread
itch. That breadth of possibilities
really highlights why a good history and a careful
(09:00):
examination are absolutely essential.
Let's look at the bigger picture, then.
Epidemiology, Where and who is most affected globally, and
maybe more specifically in places like the UK.
Globally the prevalence varies hugely, often linked to those
socio economic factors we talkedabout earlier.
In the UK, scabies is actually pretty common and occurs in both
(09:20):
the general community and frequently in institutions.
And which institutions tend to be hotspots?
Well, nursing homes, schools andprisons are the well recognised
settings for outbreaks. Again, it's down to close
contact and potential difficultyin prompt diagnosis and
treatment across everyone, right?
Looking at UK demographics, somestudies show it's somewhat more
frequently diagnosed in females,and particularly in the sort of
(09:43):
10 to 19 age group. It also tends to be more common
in areas with higher levels of deprivation and during winter
months, possibly linked to people just spending more time
indoors close together. All those factors that
facilitate that close contact. OK, let's transition now to what
you're actually going to see andhear from a patient you suspect
might have scabies, the clinicalfeatures.
(10:03):
Right. The absolute hallmark symptom,
as we've emphasised, is intense pruritus, severe itching.
The classic history you'll hear is that it's worse at night,
often bad enough to disrupt sleep significantly.
And remember that delay. Yes, remember that crucial
point. This intense itch often starts
about four to six weeks after the initial infestation, not
(10:25):
straight away. And just as importantly, the
itch can persist for several weeks even after successful
treatment because that allergic reaction takes time to settle
down. That's a really, really
important piece of information to give a patient when you treat
them, isn't it? Otherwise they might think the
treatment hasn't worked. Exactly right.
Managing expectations is absolutely key.
(10:46):
Now, the rash itself, it's typically widespread and
consists of small red raised bumps.
We call them papules, sometimes tiny blisters or vesicles or
even pustules, and it tends to appear in quite characteristic
locations. Are there specific places you
should always make sure to checkcarefully?
Yes, definitely. You want to look for lesions and
signs in the interdigital web spaces.
(11:08):
That's between the fingers, the wrists, elbows, armpits, the
waistline or belt area, the genital area and the buttocks.
Now, for infants and young children, the distribution can
differ significantly. They can commonly have lesions
on the face, scalp, neck, palms and soles, areas that are less
typically affected in adults. That's a good paediatric
(11:29):
distinction to keep in mind and the most telling sign on
examination the thing you reallywant to find.
Well, the absolute diagnostic sign, if you can find it, is the
presence of Burrows. These are the actual tunnels
created by the female mite. In the skin they appear as fine,
slightly raised, WAVY lines. They might look greyish, dark or
silvery, and they're usually quite short, typically between 2
(11:51):
and 15 millimetres long. Where should you look really
closely for these Burrows? Prime locations are those
interdigital web spaces, again the sides of the fingers and
hands, the wrists. Sometimes you can see them on
the aerial eye in females, and importantly on the male
genitalia. You might also see what's called
the wake sign. That's the Burrow ending in a
tiny papule or vesicle where themite is located, almost like a
(12:13):
tiny trail ending with the creature itself.
Like a microscopic snail trail under the skin.
Precisely. Yeah.
An itchy microscopic snail trail.
Another sign to look out for arescabies nodules.
These are firm, reddish brown lumps, often intensely itchy
themselves, typically found on the elbows, in the anterior
axillary folds, the armpits, andon the penis and scrotum.
(12:36):
Right. These nodules are also a
manifestation of a chronic allergic reaction and can
persist for months after the mites are actually gone, even
after successful treatment. So persistent nodules, just like
persistent itch, don't necessarily mean the treatment
has failed either. Correct.
They're just a sign of that lingering immune response.
Now, all that intense itching inevitably leads to secondary
(12:57):
problems, as you can imagine. I can well imagine scratching
must break the skin barrier. Exactly.
Excoriation marks, just scratch marks, are almost always
present. This constant scratching can
also exacerbate pre-existing skin conditions like eczema.
And crucially, those breaks in the skin surface are perfect
entry points for bacteria. Leading to infections.
Yes, leading to secondary bacterial infections like
(13:19):
impedigo, which you'd see as crusting lesions or even
Cellulitis. You might see the original
papules or vesicles become infected, turning into pustules
or larger crusts. OK, this brings us nicely to
that critical, more severe variant we mentioned, crusted
scabies, sometimes called Norwegian scabies.
This sounds like a completely different beast altogether.
It really is, yeah. This is a hyper infestation,
(13:41):
meaning the affected individual is carrying thousands, possibly
even millions of mites in the outer layers of their skin mixed
in with the scale. It's a really high yield area
for revision because it occurs in specific populations and has
a very different appearance and frankly a much worse prognosis
if not managed properly. Who is most vulnerable to
(14:02):
developing this crested form? The most susceptible individuals
are those who are immunosuppressed or
immunodeficient. So think patients with advanced
HIV, AIDS, those with leukaemia or lymphoma, or individuals on
long term immunosuppressant medication like after a
transplant. Also the elderly, particularly
those with cognitive impairment like dementia or individuals
with neurological conditions that reduce sensation or
(14:24):
mobility are also at increased risk.
Malnutrition is another factor. Basically, their bodies can't
mount an effective immune response to keep the mite
population under control. And what does it actually look
like? Does it still have those typical
Burrows? It looks very very different
from typical scabies. Instead of small bumps and maybe
visible Burrows, you see widespread thick, scaly crusted
(14:47):
lesions covering the skin surface.
It commonly affects the hands and feet, including the nails,
causing thickening and discoloration, the scalp and the
ears, but it can literally coverthe entire body in severe cases.
And because the sheer amount of scale and crusting, those
classic Burrows are often completely obscured, not visible
at all. So you could easily mistake it
for something like severe psoriasis or another chronic
(15:10):
scaly skin condition. Absolutely.
Misdiagnosis is unfortunately common if you're not
specifically thinking about it, especially in those at risk
groups. Associated systemic features can
sometimes include generalised lymphedonopathy, swollen lymph
nodes, and eosinophilia, which is an increased count of
eosinophils, the type of white blood cell often elevated in
(15:31):
allergic or parasitic conditions, and the.
Complications seem much more severe with crested scabies too.
Critically so, yes. The thick crusts often develop
beep fissures, cracks in the skin, which are major entry
points for bacteria. A significant, potentially life
threatening complication of crested scabies is severe
secondary bacterial infection leading to sepsis, right?
(15:53):
It's also highly, highly contagious, much more so than
typical scabies. Because of the sheer number of
mites, and it's notoriously difficult to treat.
Patients often require isolationto prevent spread.
Right, definitely a distinct andvery serious entity to be aware
of. So given all these potential
appearances from typical to Crested, how do we definitively
confirm a diagnosis? What investigations are
(16:14):
actually? Helpful.
Well, the cornerstone is always going to be clinical evaluation,
a thorough history focusing on that itch in contacts and a
careful physical examination looking for those characteristic
signs and distributions we discussed.
But what if you can't find a borough or the presentation is a
bit atypical or tricky? Yeah, that happens.
Then you move to more definitivetests if possible.
(16:38):
The gold standard is microscopicexamination.
You gently scrape a suspicious lesion, particularly the end of
a suspected Burrow if you can see one.
Place the scraping on a slide with a drop of mineral oil or
maybe potassium hydroxide, and then examine it under
microscope. And what are you looking for?
You're looking for the actual mites.
They're eggs or mite faecal matter, those little pellets
(16:59):
called sabala. Seeing any of these confirms the
diagnosis definitively. Are there other ways to
visualise things, perhaps less invasively?
Yes, dermatoscopy can be very helpful.
This involves using a handheld magnification tool like a
dramatoscope, often with polarised light.
It allows you to visualise structures within the skin's
surface layers much more clearly, making it easier to
(17:22):
identify subtle Burrows or sometimes even the mite itself
that often looks like a tiny dark triangle at the end of the
Burrow, the delta wing sign. There's also the simple ink
Burrow test. You rub some fountain pen ink,
for example, over an area where you suspect Burrows, then firmly
wipe the skin surface clean withan alcohol swab.
If a Burrow is present, the ink will track down into the tunnel
(17:43):
and remain, appearing as a fine dark WAVY line that wasn't
obvious before. Those sound like really useful
practical steps, especially the ink test.
The sources also mentioned some structured diagnostic criteria.
Yes, the International Alliance for the Control of Scabies, or
IACS, developed criteria back in2018.
The aim was to standardise diagnosis, especially for
clinical studies or situations where you can't easily get
(18:06):
microscopic confirmation. They define different levels of
certainty. So first is confirmed scabies.
This is the highest level. It's achieved by seeing a mite,
eggs or faecal matter via microscopy, dermatoscopy or
maybe other imaging techniques. This is the definitive,
confirmed diagnosis. Then there's clinical scabies.
This diagnosis is made based purely on clinical signs.
(18:28):
When you don't have that microscopic confirmation, it
requires idle, the unequivocal presence of Burrows seen on
examination or characteristic lesions found in typical
locations, plus a history of typical itching and contact with
a confirmed or suspected case. You can also be diagnosed based
on finding specific typical lesions on the male genitalia.
Right. And the third level.
(18:49):
The third is suspected scabies. This is the lowest level of
certainty. It's based on seeing typical
lesions and characteristic sites, plus having a relevant
history. So the itching in the contact
history or seeing atypical lesions in any location, but
having both a history of itchingand a history of contact with a
confirmed or suspected case. That structured approach seems
really helpful for classifying cases, especially when things
(19:10):
aren't completely clear cut. Let's quickly try and apply that
framework. Imagine a patient comes in
intensely itchy, widespread rash, but it's mostly on their
trunk and legs. Less classic sites maybe?
You can't find any definite Burrows on examination.
However, they report that their grandchild who visits them
frequently was recently diagnosed with scabies and this
(19:32):
itching is definitely keeping them awake at night.
How would you classify this using those IACS criteria?
OK, that's a good scenario. So based on those criteria,
given the atypical distribution of the rash, but the presence of
both key historical features that intense itching and close
contact with a confirmed case, this would fit the criteria for
suspected scabies. You don't have microscopic
(19:54):
confirmation or visible Burrows for confirmed or clinical
scabies, and the distribution isatypical.
But that strong history moves itbeyond just being an undiagnosed
rash. Really highlights the importance
of digging deep into that contact history, doesn't it?
It absolutely does shows how those criteria work in practise.
Yeah. OK, so once we've made the
diagnosis or have strong suspicion, how do we actually
(20:17):
treat it? Let's talk management.
Right, the absolute non negotiable golden rule of
scabies management is that you must treat all household
members, other close physical contacts and any sexual contact
simultaneously, regardless of whether they currently have
symptoms or not. Why is treating everyone at the
exact same time so critical? Well, because if you only treat
(20:39):
the person who presents, but their partner or housemaid or
close family member is also infested, maybe asymptomatically
or just in that early 46 week window before itching starts,
the treated person will simply get reinfected almost
immediately from the untreated contact.
OK, ping pong effect. Exactly, you have to break the
Chan transmission for everyone potentially exposed all at once.
(21:01):
Treat everyone simultaneously. Got it.
What's the primary treatment itself?
The standard approach is topicalapplication of a parasiticidal
cream or liquid and this needs to be applied meticulously to
the entire body surface. An entire body?
You mean literally head to toe? Pretty much.
For adults, it's usually recommended from the neck down,
but crucially for infants, youngchildren and anyone who's
(21:23):
immunocompromised who are at risk of scalp involvement or
crusted scabies. It must be applied to the face
and scalp as well-being careful to avoid the eyes and mouth.
It needs to cover every single inch of skin, including behind
the ears, palms, soles, between all fingers and toes.
And you should use a brush to get the cream under the
fingernails and toenails. And the product instructions
(21:45):
have to be followed precisely regarding how long to leave it
on. Typically it's left on overnight
for 8 to 12 hours before washingit off thoroughly.
Which topical treatments are generally recommended first?
According to current guidance like then they say CKS here in
the UK the first line treatment is Permethrin 5% dermal cream.
It's considered very effective and generally has a good safety
(22:05):
profile. And if Permethrin isn't suitable
for some reason. Yeah, if Permethrin isn't
suitable, perhaps due to a knownallergy or maybe concerns about
resistance, although that's less, it's common.
The second line option is usually Melantheon .5% aqueous
liquid. OK, and what about dealing with
that intense, persistent itching?
The treatment kills the mites, but the itch lingers, right?
(22:25):
Exactly. The itching often needs to be
treated separately from the mites themselves because it
takes time to settle. You can use topical cortamatin
10% cream or lotion which has some specific anti itch
properties. Oral antihistamines are very
helpful, especially sedating ones taken at night to help with
that sleep disruption. Low dose topical corticosteroid
(22:47):
creams can also be used consciously for localised,
particularly inflamed areas, butyou want to avoid prolonged use
or applying them to large areas.And again, you must reiterate to
the patient that the itch will likely persist for potentially
several weeks after successful mite eradication just due to
that ongoing allergic reaction. Right, manage those expectations
and for the really challenging, crusted scabies is topical.
(23:11):
Enough No Crusted scabies has such an incredibly high mite
burden that topical local treatments alone are usually
insufficient to clear it. The treatment of choice is oral
Ivermectin, which is an anti parasitic drug.
This usually requires specialistadvice, often from dermatology
or infectious disease specialists.
It might involve multiple doses of ivermectin, sometimes
(23:31):
combined with topical agents as well, and often needs to be
managed in a hospital setting with appropriate isolation
precautions to prevent spread. Makes sense.
Beyond the medication itself, are there essential hygiene
measures people need to take? Absolutely.
These are really key and are considered part of the overall
treatment plan. On the day the first treatment
is applied, all clothing, towelsand bed linen that have been
(23:54):
used by the infested person in the previous, say, 3 days should
be machine wash at a hot cycle at least 50°C or 122 Fahrenheit.
And what about items that can't be washed easily, like shoes or
soft toys? Good question.
Items that cannot be washed, like certain shoes, coats or
stuffed animals should be sealedtightly in plastic bags for at
(24:15):
least 72 hours, 3 full days. That's sufficient time to kill
any mites that might have fallenoff the body and can't survive
away from a human host for long.Do you need to go crazy
disinfecting the entire house oruse special insecticide sprays?
No, definitely not. Fumigation or extensive chemical
cleaning of the house is not necessary and generally not
recommended. Routine cleaning with standard
(24:38):
household products is sufficientfor surfaces like floors and
furniture. Vacuuming carpeted floors and
any upholstered furniture that the person is used frequently is
also a good idea. OK so just to recap the core
treatment protocol then Permethrin 5% first line or
Malatheon 0.5% applied to the whole body neck down for most
adults but include face scout for children Immunocompromised.
(25:01):
Leave it on as directed, usuallyovernight, and crucially, you
mentioned repeating the application.
Yes, repeating the application after 7 to 10 days.
The exact timing might vary slightly by guideline, but
around a week later is absolutely essential.
Why the repeat treatment? Because the first application
kills the live mites and maybe newly hatched larvae, but it
(25:22):
typically does not reliably killthe eggs that are already laid
within the Burrows. Repeating the treatment about a
week later ensures that any mites which have hatched since
the first treatment but before they've had a chance to mature
and lay new eggs, are also killed off.
Breaking the life cycle? Exactly.
It's necessary for successful eradication.
Oral ivermectin, as we said, is an alternative, especially if
(25:43):
topical treatment is difficult or contraindicated.
And of course you need oral antibiotics if there are signs
of secondary bacterial infection.
What if you're dealing with an outbreak situation, like in a
nursing home or a prison? That requires prompt
notification to the local publichealth authorities or infection
control team. They will help coordinate mass
treatment protocols for all residents and staff involved to
(26:05):
control the outbreak effectivelyand stop it spreading further.
And one final point on management.
Because scabies can be sexually transmitted, it's generally
considered good practise to offer full STI screening
individuals diagnosed with it asthey may have acquired other
infections concurrently. That's a very good clinical
Pearl to remember. So what can patients generally
(26:27):
expect after treatment? What's the prognosis like?
Well, with correct diagnosis andstrict adherence to that
treatment protocol, especially treating the patient and all
contacts simultaneously and repeating the treatment, the
prognosis is generally excellent.
The infestation can be successfully eliminated, but
the. Itch might hang around for a
bit. Yes, absolutely emphasise that
(26:49):
to the patient. The itching and potentially
those noggles we mentioned can persist for several weeks,
sometimes even a couple of months after all the mites are
completely gone. It's just due to that lingering
allergic reaction in the skin, right?
It doesn't mean the treatment failed, just that the body's
immune response is taking time to fully calm down.
What's the biggest risk, then, to a successful outcome?
What causes treatment failure usually?
(27:12):
The major risk by far is reinfection.
This almost always happens if not all contacts are treated
properly and simultaneously, or if those environmental measures
like washing bedding aren't donecorrectly, or if the treatment
wasn't applied meticulously enough or wasn't repeated.
So compliance is key. Compliance and thoroughness are
absolutely key. Prompt treatment for everyone
(27:33):
exposed is vital to break that chain of transmission
permanently. Now for crested scabies,
especially in those with underlying immunosuppression,
treatment could be much more complex.
It might require longer courses or combinations of treatments,
and the prognosis really dependsheavily on managing the
underlying condition as well. And finally, what are the
potential complications if scabies is left untreated or in
(27:57):
those more severe cases? OK.
The most common complications aswe've touched upon are those
secondary bacterial skin infections resulting from all
the scratching. Impedigo and Cellulitis are
pretty frequent. And crested scabies itself is
considered a severe complication.
Yes, you can think of crested scabies as both a severe
manifestation and a complicationthat occurs in vulnerable, often
(28:18):
immunosuppressed individuals. As we detailed, it presents with
those thick, widespread crusts and carries a much higher risk
of further complications. Like really serious infections.
Exactly secondary bacterial infections in crested scabies
can be much more serious, potentially leading to skin
abscesses or even progressing tobacteremia and sepsis, which can
(28:40):
of course be life threatening. Other complications include the
persistent scabies nodules we discussed, sometimes extensive
dermatitis covering large areas of the body, occasionally
progressing to erythroderma, which is widespread redness and
scaling of almost the entire skin surface, and not
insignificantly significant psychological distress.
(29:00):
This could be due to the severe itch, the chronic sleep
deprivation and sometimes the potential social stigma
associated with having scabies. That's a really comprehensive
look at scabies, from that tiny mite causing all the trouble
right through to the potentiallysevere complications.
Yeah, I think we've covered the main points for revision, the
definition, how it spreads via contact, who's most at risk, the
(29:22):
underlying mechanism of that allergic itch, what you'll see
clinically, especially those Burrows and nodules and the
different distribution of kids. How to diagnose it using
clinical signs, microscopy and those IACS criteria?
And the essential management principles, especially treating
all contacts simultaneously, repeating the treatment, the
hygiene measures and importantly, being aware of that
(29:42):
severe crested scabies variant and who is most vulnerable to
it. Absolutely critical points for
anyone revising, so let's maybe leave you the listener with this
thought to consider. Given how varied the
presentation of scabies can actually be, especially with
atypical lesions or those delayed symptoms, and
considering how many other issuerashes exist, how often might
(30:03):
scabies actually be missed on aninitial assessment, particularly
in busy clinical settings or perhaps in patients who don't
perfectly fit the classic demographic profile?
That's a good point. It truly underscores the
importance of keeping scabies onyour differential diagnosis list
for pretty much any unexplained itchy rash and really taking the
time to ask carefully about potential contacts.
(30:23):
Indeed. Well, that wraps up our deep
dive into scabies for MSRA revision.
For more free MSRA revision resources, do visit
freem-sra.com and for the full Premium Revision Toolkit, head
over to pass them sra.com.
OK, picture this. You're hitting the books late,
trying to cram, but your skin isjust crawling.
The itching is relentless. It's driving you absolutely mad,
especially when you're warm or trying to sleep at night.
It's not just irritating, it feels like something's actually
under your skin. What could possibly be causing
(00:21):
this intense torment? Yeah, that sounds like a really
classic presentation of scabies.It's one of those conditions
that's, well more common than you might think.
Yeah, just incredibly uncomfortable for the person
going through it. And that's exactly what we're
unpacking today. Welcome to this deep dive
focused entirely on scabies. Our mission is specifically
tailored for you. If you're revising for exams,
(00:43):
you know like the MSRA, we want to give you a high yield focused
overview straight from the source material.
Exactly. We're going to slice through the
details to give you the essential knowledge what scabies
actually is, where it comes from, who's most vulnerable,
what it looks and feels like right, how you figure out if
someone has it in practise and crucially, how to effectively
treat it and, you know, stop it coming back.
(01:04):
Think of this as distilling all that key information into a
concise session designed to really stick in your mind.
Let's jump right in. So at its heart, what exactly is
scabies? OK, at its core, scabies is a
skin infestation. It's caused by a tiny little
parasitic creature, the Sarcopti's Scabiomite, and it's
highly contagious. So a mite is causing the problem
(01:27):
and the main symptoms people complain about.
Well, the defining features you'll see and hear about are
that intense itching, the puritus you just described, and
a characteristic rash. Now here's a really important
point, a key takeaway for revision the intense itching and
the rash. They are primarily caused by the
mite. Just like crawling around.
(01:47):
They're actually your body's allergic or hypersensitivity
reaction to the mites themselves, their eggs and their
waste products. Their faeces burned in the skin.
OK, so it's not the physical sensation of the mites so much
as your immune system reacting to these tiny invaders and,
well, what they leave behind. Spot on.
That immune response is what drives the intense inflammation
(02:08):
in that awful itch. And you know, while we might
associate it with certain stereotypes, scabies can affect
anyone, anywhere. It spreads primarily through
close, direct skin to skin contact, right?
The female mite needs to Burrow into the top layer of your skin,
the epidermis, to lay her eggs. OK, so it's an infestation
(02:29):
causing an allergic reaction spreading via close contact.
Let's get a bit more specific about the cause and how it
works. The aetiology.
What species are we talking about here?
Yeah, it's caused specifically by the Sarcoptis KBMI variety
hominis. This one's adapted specifically
to humans and the female might she's the the engineer here.
She tunnels into the stratum corneum that's at the very top
(02:50):
layer of your epidermis, creating those characteristic
Burrows. And she's doing more than just
tunnelling while she's in there.Oh.
Absolutely. As she tunnels along, she lays
eggs along the Burrow. Those eggs take about 10 to 15
days to mature. Once they hatch, the new mites
emerge onto the skin surface, They mature, they mate, and the
whole cycle just continues. An adult mite lives for about
(03:12):
four to six weeks. That's quite a life cycle
happening right under the skin surface.
How much contact is actually needed for transmission?
Is it just like a brief touch? Well, for typical scabies
transmission usually requires prolonged direct skin to skin
contact. The sources suggest this is
generally around 10 to 15 minutes of sustained contact.
(03:33):
OK. However, there's a really
important exception, especially clinically crested scabies.
Ah, the really severe form we hear about.
Precisely, in crested scabies, individuals have a
hyperinfestation. We're talking thousands, maybe
even millions of mites. Because of this incredibly high
might load, transmission is much, much easier.
(03:53):
It can occur via contaminated items like bedding, clothing or
furniture, which is pretty uncommon in typical scabies.
And there's a crucial point about the timing of symptoms
that's so vital for history taking, isn't there?
The itching doesn't just appear overnight after you've been
exposed. This is a super high yield
detail for exams and well for practise to the intense itching
(04:14):
that Puritus. It typically has a significant
delay, usually starts about fourto six weeks after the initial
infestation. Four to six weeks.
Why such a long delay? Well, because that's roughly how
long it takes for your body to develop the allergic
sensitization to the mites and all their products.
The immune system has to learn to react.
So someone could actually be infested, potentially spreading
(04:37):
mites around for over a month before they even develop the
main symptom that brings them toa doctor.
Exactly. And asymptomatic transmission is
also possible, which just adds another layer of complexity to
controlling outbreaks, doesn't it?
Yeah, definitely. It really highlights the need
for a high index of suspicion, especially in potential exposure
settings. That delayed reaction is
absolutely key to understanding its spread.
(04:59):
So who is most likely to get it?What are the major risk factors
we should be aware of? OK, several factors increase
susceptibility. Crowded living conditions are a
primary one, obviously, as they increase the likelihood of that
prolonged skin to skin contact needed for transmission.
Makes sense? Frequent physical contact with
infested individuals is, well, obviously a direct risk, and
(05:20):
while it's not the sole Causeway, poor hygiene can
sometimes contribute, maybe in the sense of delayed recognition
or perhaps a more severe resentation.
But it's really crucial to remember scabies can affect
anyone, regardless of how clean they are.
And certain locations just seem like perfect breeding grounds
for outbreaks, don't they? Absolutely, institutional
settings are the classic examples.
(05:42):
Nursing homes, prisons, childcare facilities, basically
anywhere people live or spend extended periods in close
proximity. Right.
Socio economic factors are also strongly linked.
Things like poverty, living in refugee camps, malnutrition and
homelessness are all significantrisk factors.
Dementia is listed as well, I noticed.
Yes, that's likely due to factors like reduced self-care
(06:05):
capacity or maybe difficulty communicating symptoms early on.
Sexual contact is another well documented route of
transmission. OK.
And certain populations are particularly vulnerable
children, especially in developing countries where
prevalence can be very high and critically immunodeficient or
immunosuppressed individuals. Like patients with HIV or those
(06:27):
on immunosuppressant therapy? Exactly those groups, their
compromised immune response can lead to much, much more severe
infestations like that crusted scabies we mentioned.
All these risk factors together explain why outbreaks can spread
so rapidly and vulnerable or overcrowded communities.
So we know what the mite is and how it gets around.
How does it actually cause the problems we see and feel?
(06:49):
Let's dive into the pathophysiology a bit, OK?
It all starts with that female mite burrowing into the upper
layers of the skin, the epidermis.
She then lays her eggs along thetunnel she creates as she goes.
And this is where the body's reaction really kicks in.
Precisely. The mites, saliva, the eggs she
lays and the faecal pellets the sabala left in the Burrow act as
(07:10):
foreign antigens. Your immune system recognises
these and mounts what's called the delayed type
hypersensitivity reaction. OK.
This is essentially an allergic inflammatory response happening
within the skin itself. So the intense itching and that
rash we see are basically manifestations of that localised
allergic inflammation. That's the key mechanism, yeah.
(07:32):
It's your body sort of overreacting to the presence of
the mites and their waste products just under the skin
surface. And as the eggs hatch, new mites
mature, create new Burrows, deposit more antigens.
This. Cycle just keeps going.
Exactly. The cycle of infestation and
allergic response continues, which is why the symptoms
persist and often get worse if it's not.
Treated. That makes perfect sense.
Your body is constantly fightingthese tiny invaders and their
(07:55):
leftovers, as you put it. Now that description, an icky
rash could fit a whole lot of conditions.
What else should be on our radarwhen we're thinking about
scabies? The differential diagnosis.
Yeah, this is a really critical area for diagnosis and for
exams, too. Scabies can be a great mimicker.
You definitely need to consider common itchy rashes like insect
(08:15):
bites. You know, various forms of
eczema, atopic contact dermatitis.
The usual suspects. Right, and fungal skin
infections like teeny corpus. Also don't forget secondary
issues that arise from all the scratching like impedigo or
other bacterial skin infections.Other possibilities on your
differential might include conditions like like blandness
or psoriasis, although their appearance is often quite
(08:38):
distinct if you look closely. Less commonly, perhaps in
widespread or atypical cases, one might even consider things
like bullispimphegoid or certainsystemic conditions causing a
rash, but they usually have other prominent features.
So a broad list. Yeah, the core task is always
differentiating it from the morecommon causes of widespread
itch. That breadth of possibilities
really highlights why a good history and a careful
(09:00):
examination are absolutely essential.
Let's look at the bigger picture, then.
Epidemiology, Where and who is most affected globally, and
maybe more specifically in places like the UK.
Globally the prevalence varies hugely, often linked to those
socio economic factors we talkedabout earlier.
In the UK, scabies is actually pretty common and occurs in both
(09:20):
the general community and frequently in institutions.
And which institutions tend to be hotspots?
Well, nursing homes, schools andprisons are the well recognised
settings for outbreaks. Again, it's down to close
contact and potential difficultyin prompt diagnosis and
treatment across everyone, right?
Looking at UK demographics, somestudies show it's somewhat more
frequently diagnosed in females,and particularly in the sort of
(09:43):
10 to 19 age group. It also tends to be more common
in areas with higher levels of deprivation and during winter
months, possibly linked to people just spending more time
indoors close together. All those factors that
facilitate that close contact. OK, let's transition now to what
you're actually going to see andhear from a patient you suspect
might have scabies, the clinicalfeatures.
(10:03):
Right. The absolute hallmark symptom,
as we've emphasised, is intense pruritus, severe itching.
The classic history you'll hear is that it's worse at night,
often bad enough to disrupt sleep significantly.
And remember that delay. Yes, remember that crucial
point. This intense itch often starts
about four to six weeks after the initial infestation, not
(10:25):
straight away. And just as importantly, the
itch can persist for several weeks even after successful
treatment because that allergic reaction takes time to settle
down. That's a really, really
important piece of information to give a patient when you treat
them, isn't it? Otherwise they might think the
treatment hasn't worked. Exactly right.
Managing expectations is absolutely key.
(10:46):
Now, the rash itself, it's typically widespread and
consists of small red raised bumps.
We call them papules, sometimes tiny blisters or vesicles or
even pustules, and it tends to appear in quite characteristic
locations. Are there specific places you
should always make sure to checkcarefully?
Yes, definitely. You want to look for lesions and
signs in the interdigital web spaces.
(11:08):
That's between the fingers, the wrists, elbows, armpits, the
waistline or belt area, the genital area and the buttocks.
Now, for infants and young children, the distribution can
differ significantly. They can commonly have lesions
on the face, scalp, neck, palms and soles, areas that are less
typically affected in adults. That's a good paediatric
(11:29):
distinction to keep in mind and the most telling sign on
examination the thing you reallywant to find.
Well, the absolute diagnostic sign, if you can find it, is the
presence of Burrows. These are the actual tunnels
created by the female mite. In the skin they appear as fine,
slightly raised, WAVY lines. They might look greyish, dark or
silvery, and they're usually quite short, typically between 2
(11:51):
and 15 millimetres long. Where should you look really
closely for these Burrows? Prime locations are those
interdigital web spaces, again the sides of the fingers and
hands, the wrists. Sometimes you can see them on
the aerial eye in females, and importantly on the male
genitalia. You might also see what's called
the wake sign. That's the Burrow ending in a
tiny papule or vesicle where themite is located, almost like a
(12:13):
tiny trail ending with the creature itself.
Like a microscopic snail trail under the skin.
Precisely. Yeah.
An itchy microscopic snail trail.
Another sign to look out for arescabies nodules.
These are firm, reddish brown lumps, often intensely itchy
themselves, typically found on the elbows, in the anterior
axillary folds, the armpits, andon the penis and scrotum.
(12:36):
Right. These nodules are also a
manifestation of a chronic allergic reaction and can
persist for months after the mites are actually gone, even
after successful treatment. So persistent nodules, just like
persistent itch, don't necessarily mean the treatment
has failed either. Correct.
They're just a sign of that lingering immune response.
Now, all that intense itching inevitably leads to secondary
(12:57):
problems, as you can imagine. I can well imagine scratching
must break the skin barrier. Exactly.
Excoriation marks, just scratch marks, are almost always
present. This constant scratching can
also exacerbate pre-existing skin conditions like eczema.
And crucially, those breaks in the skin surface are perfect
entry points for bacteria. Leading to infections.
Yes, leading to secondary bacterial infections like
(13:19):
impedigo, which you'd see as crusting lesions or even
Cellulitis. You might see the original
papules or vesicles become infected, turning into pustules
or larger crusts. OK, this brings us nicely to
that critical, more severe variant we mentioned, crusted
scabies, sometimes called Norwegian scabies.
This sounds like a completely different beast altogether.
It really is, yeah. This is a hyper infestation,
(13:41):
meaning the affected individual is carrying thousands, possibly
even millions of mites in the outer layers of their skin mixed
in with the scale. It's a really high yield area
for revision because it occurs in specific populations and has
a very different appearance and frankly a much worse prognosis
if not managed properly. Who is most vulnerable to
(14:02):
developing this crested form? The most susceptible individuals
are those who are immunosuppressed or
immunodeficient. So think patients with advanced
HIV, AIDS, those with leukaemia or lymphoma, or individuals on
long term immunosuppressant medication like after a
transplant. Also the elderly, particularly
those with cognitive impairment like dementia or individuals
with neurological conditions that reduce sensation or
(14:24):
mobility are also at increased risk.
Malnutrition is another factor. Basically, their bodies can't
mount an effective immune response to keep the mite
population under control. And what does it actually look
like? Does it still have those typical
Burrows? It looks very very different
from typical scabies. Instead of small bumps and maybe
visible Burrows, you see widespread thick, scaly crusted
(14:47):
lesions covering the skin surface.
It commonly affects the hands and feet, including the nails,
causing thickening and discoloration, the scalp and the
ears, but it can literally coverthe entire body in severe cases.
And because the sheer amount of scale and crusting, those
classic Burrows are often completely obscured, not visible
at all. So you could easily mistake it
for something like severe psoriasis or another chronic
(15:10):
scaly skin condition. Absolutely.
Misdiagnosis is unfortunately common if you're not
specifically thinking about it, especially in those at risk
groups. Associated systemic features can
sometimes include generalised lymphedonopathy, swollen lymph
nodes, and eosinophilia, which is an increased count of
eosinophils, the type of white blood cell often elevated in
(15:31):
allergic or parasitic conditions, and the.
Complications seem much more severe with crested scabies too.
Critically so, yes. The thick crusts often develop
beep fissures, cracks in the skin, which are major entry
points for bacteria. A significant, potentially life
threatening complication of crested scabies is severe
secondary bacterial infection leading to sepsis, right?
(15:53):
It's also highly, highly contagious, much more so than
typical scabies. Because of the sheer number of
mites, and it's notoriously difficult to treat.
Patients often require isolationto prevent spread.
Right, definitely a distinct andvery serious entity to be aware
of. So given all these potential
appearances from typical to Crested, how do we definitively
confirm a diagnosis? What investigations are
(16:14):
actually? Helpful.
Well, the cornerstone is always going to be clinical evaluation,
a thorough history focusing on that itch in contacts and a
careful physical examination looking for those characteristic
signs and distributions we discussed.
But what if you can't find a borough or the presentation is a
bit atypical or tricky? Yeah, that happens.
Then you move to more definitivetests if possible.
(16:38):
The gold standard is microscopicexamination.
You gently scrape a suspicious lesion, particularly the end of
a suspected Burrow if you can see one.
Place the scraping on a slide with a drop of mineral oil or
maybe potassium hydroxide, and then examine it under
microscope. And what are you looking for?
You're looking for the actual mites.
They're eggs or mite faecal matter, those little pellets
(16:59):
called sabala. Seeing any of these confirms the
diagnosis definitively. Are there other ways to
visualise things, perhaps less invasively?
Yes, dermatoscopy can be very helpful.
This involves using a handheld magnification tool like a
dramatoscope, often with polarised light.
It allows you to visualise structures within the skin's
surface layers much more clearly, making it easier to
(17:22):
identify subtle Burrows or sometimes even the mite itself
that often looks like a tiny dark triangle at the end of the
Burrow, the delta wing sign. There's also the simple ink
Burrow test. You rub some fountain pen ink,
for example, over an area where you suspect Burrows, then firmly
wipe the skin surface clean withan alcohol swab.
If a Burrow is present, the ink will track down into the tunnel
(17:43):
and remain, appearing as a fine dark WAVY line that wasn't
obvious before. Those sound like really useful
practical steps, especially the ink test.
The sources also mentioned some structured diagnostic criteria.
Yes, the International Alliance for the Control of Scabies, or
IACS, developed criteria back in2018.
The aim was to standardise diagnosis, especially for
clinical studies or situations where you can't easily get
(18:06):
microscopic confirmation. They define different levels of
certainty. So first is confirmed scabies.
This is the highest level. It's achieved by seeing a mite,
eggs or faecal matter via microscopy, dermatoscopy or
maybe other imaging techniques. This is the definitive,
confirmed diagnosis. Then there's clinical scabies.
This diagnosis is made based purely on clinical signs.
(18:28):
When you don't have that microscopic confirmation, it
requires idle, the unequivocal presence of Burrows seen on
examination or characteristic lesions found in typical
locations, plus a history of typical itching and contact with
a confirmed or suspected case. You can also be diagnosed based
on finding specific typical lesions on the male genitalia.
Right. And the third level.
(18:49):
The third is suspected scabies. This is the lowest level of
certainty. It's based on seeing typical
lesions and characteristic sites, plus having a relevant
history. So the itching in the contact
history or seeing atypical lesions in any location, but
having both a history of itchingand a history of contact with a
confirmed or suspected case. That structured approach seems
really helpful for classifying cases, especially when things
(19:10):
aren't completely clear cut. Let's quickly try and apply that
framework. Imagine a patient comes in
intensely itchy, widespread rash, but it's mostly on their
trunk and legs. Less classic sites maybe?
You can't find any definite Burrows on examination.
However, they report that their grandchild who visits them
frequently was recently diagnosed with scabies and this
(19:32):
itching is definitely keeping them awake at night.
How would you classify this using those IACS criteria?
OK, that's a good scenario. So based on those criteria,
given the atypical distribution of the rash, but the presence of
both key historical features that intense itching and close
contact with a confirmed case, this would fit the criteria for
suspected scabies. You don't have microscopic
(19:54):
confirmation or visible Burrows for confirmed or clinical
scabies, and the distribution isatypical.
But that strong history moves itbeyond just being an undiagnosed
rash. Really highlights the importance
of digging deep into that contact history, doesn't it?
It absolutely does shows how those criteria work in practise.
Yeah. OK, so once we've made the
diagnosis or have strong suspicion, how do we actually
(20:17):
treat it? Let's talk management.
Right, the absolute non negotiable golden rule of
scabies management is that you must treat all household
members, other close physical contacts and any sexual contact
simultaneously, regardless of whether they currently have
symptoms or not. Why is treating everyone at the
exact same time so critical? Well, because if you only treat
(20:39):
the person who presents, but their partner or housemaid or
close family member is also infested, maybe asymptomatically
or just in that early 46 week window before itching starts,
the treated person will simply get reinfected almost
immediately from the untreated contact.
OK, ping pong effect. Exactly, you have to break the
Chan transmission for everyone potentially exposed all at once.
(21:01):
Treat everyone simultaneously. Got it.
What's the primary treatment itself?
The standard approach is topicalapplication of a parasiticidal
cream or liquid and this needs to be applied meticulously to
the entire body surface. An entire body?
You mean literally head to toe? Pretty much.
For adults, it's usually recommended from the neck down,
but crucially for infants, youngchildren and anyone who's
(21:23):
immunocompromised who are at risk of scalp involvement or
crusted scabies. It must be applied to the face
and scalp as well-being careful to avoid the eyes and mouth.
It needs to cover every single inch of skin, including behind
the ears, palms, soles, between all fingers and toes.
And you should use a brush to get the cream under the
fingernails and toenails. And the product instructions
(21:45):
have to be followed precisely regarding how long to leave it
on. Typically it's left on overnight
for 8 to 12 hours before washingit off thoroughly.
Which topical treatments are generally recommended first?
According to current guidance like then they say CKS here in
the UK the first line treatment is Permethrin 5% dermal cream.
It's considered very effective and generally has a good safety
(22:05):
profile. And if Permethrin isn't suitable
for some reason. Yeah, if Permethrin isn't
suitable, perhaps due to a knownallergy or maybe concerns about
resistance, although that's less, it's common.
The second line option is usually Melantheon .5% aqueous
liquid. OK, and what about dealing with
that intense, persistent itching?
The treatment kills the mites, but the itch lingers, right?
(22:25):
Exactly. The itching often needs to be
treated separately from the mites themselves because it
takes time to settle. You can use topical cortamatin
10% cream or lotion which has some specific anti itch
properties. Oral antihistamines are very
helpful, especially sedating ones taken at night to help with
that sleep disruption. Low dose topical corticosteroid
(22:47):
creams can also be used consciously for localised,
particularly inflamed areas, butyou want to avoid prolonged use
or applying them to large areas.And again, you must reiterate to
the patient that the itch will likely persist for potentially
several weeks after successful mite eradication just due to
that ongoing allergic reaction. Right, manage those expectations
and for the really challenging, crusted scabies is topical.
(23:11):
Enough No Crusted scabies has such an incredibly high mite
burden that topical local treatments alone are usually
insufficient to clear it. The treatment of choice is oral
Ivermectin, which is an anti parasitic drug.
This usually requires specialistadvice, often from dermatology
or infectious disease specialists.
It might involve multiple doses of ivermectin, sometimes
(23:31):
combined with topical agents as well, and often needs to be
managed in a hospital setting with appropriate isolation
precautions to prevent spread. Makes sense.
Beyond the medication itself, are there essential hygiene
measures people need to take? Absolutely.
These are really key and are considered part of the overall
treatment plan. On the day the first treatment
is applied, all clothing, towelsand bed linen that have been
(23:54):
used by the infested person in the previous, say, 3 days should
be machine wash at a hot cycle at least 50°C or 122 Fahrenheit.
And what about items that can't be washed easily, like shoes or
soft toys? Good question.
Items that cannot be washed, like certain shoes, coats or
stuffed animals should be sealedtightly in plastic bags for at
(24:15):
least 72 hours, 3 full days. That's sufficient time to kill
any mites that might have fallenoff the body and can't survive
away from a human host for long.Do you need to go crazy
disinfecting the entire house oruse special insecticide sprays?
No, definitely not. Fumigation or extensive chemical
cleaning of the house is not necessary and generally not
recommended. Routine cleaning with standard
(24:38):
household products is sufficientfor surfaces like floors and
furniture. Vacuuming carpeted floors and
any upholstered furniture that the person is used frequently is
also a good idea. OK so just to recap the core
treatment protocol then Permethrin 5% first line or
Malatheon 0.5% applied to the whole body neck down for most
adults but include face scout for children Immunocompromised.
(25:01):
Leave it on as directed, usuallyovernight, and crucially, you
mentioned repeating the application.
Yes, repeating the application after 7 to 10 days.
The exact timing might vary slightly by guideline, but
around a week later is absolutely essential.
Why the repeat treatment? Because the first application
kills the live mites and maybe newly hatched larvae, but it
(25:22):
typically does not reliably killthe eggs that are already laid
within the Burrows. Repeating the treatment about a
week later ensures that any mites which have hatched since
the first treatment but before they've had a chance to mature
and lay new eggs, are also killed off.
Breaking the life cycle? Exactly.
It's necessary for successful eradication.
Oral ivermectin, as we said, is an alternative, especially if
(25:43):
topical treatment is difficult or contraindicated.
And of course you need oral antibiotics if there are signs
of secondary bacterial infection.
What if you're dealing with an outbreak situation, like in a
nursing home or a prison? That requires prompt
notification to the local publichealth authorities or infection
control team. They will help coordinate mass
treatment protocols for all residents and staff involved to
(26:05):
control the outbreak effectivelyand stop it spreading further.
And one final point on management.
Because scabies can be sexually transmitted, it's generally
considered good practise to offer full STI screening
individuals diagnosed with it asthey may have acquired other
infections concurrently. That's a very good clinical
Pearl to remember. So what can patients generally
(26:27):
expect after treatment? What's the prognosis like?
Well, with correct diagnosis andstrict adherence to that
treatment protocol, especially treating the patient and all
contacts simultaneously and repeating the treatment, the
prognosis is generally excellent.
The infestation can be successfully eliminated, but
the. Itch might hang around for a
bit. Yes, absolutely emphasise that
(26:49):
to the patient. The itching and potentially
those noggles we mentioned can persist for several weeks,
sometimes even a couple of months after all the mites are
completely gone. It's just due to that lingering
allergic reaction in the skin, right?
It doesn't mean the treatment failed, just that the body's
immune response is taking time to fully calm down.
What's the biggest risk, then, to a successful outcome?
What causes treatment failure usually?
(27:12):
The major risk by far is reinfection.
This almost always happens if not all contacts are treated
properly and simultaneously, or if those environmental measures
like washing bedding aren't donecorrectly, or if the treatment
wasn't applied meticulously enough or wasn't repeated.
So compliance is key. Compliance and thoroughness are
absolutely key. Prompt treatment for everyone
(27:33):
exposed is vital to break that chain of transmission
permanently. Now for crested scabies,
especially in those with underlying immunosuppression,
treatment could be much more complex.
It might require longer courses or combinations of treatments,
and the prognosis really dependsheavily on managing the
underlying condition as well. And finally, what are the
potential complications if scabies is left untreated or in
(27:57):
those more severe cases? OK.
The most common complications aswe've touched upon are those
secondary bacterial skin infections resulting from all
the scratching. Impedigo and Cellulitis are
pretty frequent. And crested scabies itself is
considered a severe complication.
Yes, you can think of crested scabies as both a severe
manifestation and a complicationthat occurs in vulnerable, often
(28:18):
immunosuppressed individuals. As we detailed, it presents with
those thick, widespread crusts and carries a much higher risk
of further complications. Like really serious infections.
Exactly secondary bacterial infections in crested scabies
can be much more serious, potentially leading to skin
abscesses or even progressing tobacteremia and sepsis, which can
(28:40):
of course be life threatening. Other complications include the
persistent scabies nodules we discussed, sometimes extensive
dermatitis covering large areas of the body, occasionally
progressing to erythroderma, which is widespread redness and
scaling of almost the entire skin surface, and not
insignificantly significant psychological distress.
(29:00):
This could be due to the severe itch, the chronic sleep
deprivation and sometimes the potential social stigma
associated with having scabies. That's a really comprehensive
look at scabies, from that tiny mite causing all the trouble
right through to the potentiallysevere complications.
Yeah, I think we've covered the main points for revision, the
definition, how it spreads via contact, who's most at risk, the
(29:22):
underlying mechanism of that allergic itch, what you'll see
clinically, especially those Burrows and nodules and the
different distribution of kids. How to diagnose it using
clinical signs, microscopy and those IACS criteria?
And the essential management principles, especially treating
all contacts simultaneously, repeating the treatment, the
hygiene measures and importantly, being aware of that
(29:42):
severe crested scabies variant and who is most vulnerable to
it. Absolutely critical points for
anyone revising, so let's maybe leave you the listener with this
thought to consider. Given how varied the
presentation of scabies can actually be, especially with
atypical lesions or those delayed symptoms, and
considering how many other issuerashes exist, how often might
(30:03):
scabies actually be missed on aninitial assessment, particularly
in busy clinical settings or perhaps in patients who don't
perfectly fit the classic demographic profile?
That's a good point. It truly underscores the
importance of keeping scabies onyour differential diagnosis list
for pretty much any unexplained itchy rash and really taking the
time to ask carefully about potential contacts.
(30:23):
Indeed. Well, that wraps up our deep
dive into scabies for MSRA revision.
For more free MSRA revision resources, do visit
freem-sra.com and for the full Premium Revision Toolkit, head
over to pass them sra.com.
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