BrainStuff Classics: Why Does Skin Tan and Freckle?

When you freckle or tan, your skin is trying to protect you from damage. Learn how it works in this episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff, a production of I Heart Radio.
Hey brain Stuff. I'm Lauren Volga Bam and this this
is another classic episode from our archives. I'm pretty sure
this one was originally written for our earstwhile YouTube series.
It's about how our skin protects us from the sun,
or tries to by making us tan and freckle. Hey

(00:26):
brain Stuff, Lauren vog O Bam. Here when the weather
is nice, I've been made to understand that some people
enjoy spending time outdoors where they're exposed to, among other things, sunlight.
Stuff in sunlight can make stuff in your skin produce
more pigment, which shows up as freckles or a tan.
But how why? Scientifically speaking, the skin freckling tan both

(00:48):
happen in your epidermis, which is the tough, resilient frosting
on our body's cake. Under normal circumstances, it protects and
helps hold in our precious, squishy insides. Your epidermis contains
a few kinds of cells, but the ones were primarily
concerned with here are the carrotino sites and the melano sytes.
Carrotino sites make up most of your epidermis. Their skin

(01:10):
cells that are maturing and getting pushed upward towards your
skin surface by new cell growth. Melano Sytes are specialized
cells that create pigmented proteins called melanin. And by the way,
they're not only found in our skin. Melano Sytes are
also at work in your eyes and hair, giving them
their color, and in your heart, inner ear, and brain

(01:30):
doing No one is really sure what conspiring to make
you enjoy reality television maybe, but in your skin, melanocytes
produce the pigments that help give your skin its tone.
Whatever color your skin is, it contains an average of
one thousand, two hundred melanosytes per square millimeter. Your genes
and various factors in your environment tell your melanocytes how

(01:52):
much melanin to produce and what types. One of those
environmental factors is ultraviolet radiation, probably from sunlight or maybe
from black lights at raves, and cellular biology is really complicated.
To paraphrase in Ego Montoya, I'm just going to sum up.
When certain types of ultraviolet photons pass into your skin,
as specifically into your carrotino sites there and smack into

(02:15):
molecules of your DNA, those photons cause minor damage that
sets off a chain reaction. The end result, your melano
sytes go into overdrive producing melanin particles. Your melano sytes
carefully pack those melanine particles into special organelles called melanosomes,
sort of like little intercellular shipping boxes. These melanan packages

(02:35):
moved to the very edges of the melano site, and
neighboring carrotino sites bite the melanosomes right out of the
cell and absorb them. It doesn't hurt the melanosyte. It
just sounds creepy because it is okay, so you catch
some sun. If your melano sytes and therefore your melanin
packed melanosomes are spread evenly around among your carrotino sites,

(02:56):
you can, But if your melanosytes are clustered together freckle.
Either way, the melanin particles absorb incoming UV radiation and
transform it into infrared radiation, which is just low level heat. Thus,
your delicate squidgy insides and your cells DNA are protected
from further UV damage Without frequency and exposure, Tans and

(03:18):
freckles fade over time because your caroteno sites don't last forever.
As new skin cells grow and mature, your old caroteno
sites are eventually pushed to the very surface of your skin,
where they become dehydrated and die. And that's right. These
cells on the surface of our skin, the ones that
we can see and touch, are actually dead, but it's
for a good cause. During the process of drying out

(03:39):
and dyeing, your caroteno sites become the strong, durable layer
that makes our skin so effective at keeping blood in
and germs out. And when your caroteno sites move on
to that big skin layer on the surface, they bring
any melanin that they've collected along with them. And when
those cells slough off through normal wear and tear, the
melanin goes to and your skin returns to its usual pigment,

(04:02):
which in my case is translucent like a deep sea shrimp.
Today's episode isn't based on an article, but was written
by me Lauren Vogelbaum when I was writing for house
Stuff works dot com. Brain Stuff is now a production
of iHeart Radio in partnership with how stuff works dot Com,

(04:23):
and it's produced by Tyler Clang. For more podcasts my
Heart Radio, visit the iHeart Radio app, Apple Podcasts, or
wherever you listen to your favorite shows.