BrainStuff Classics: How Can Your Birth Season Determine Your Allergies?

The season you were born in helps determine whether you'll have allergies, but science has never understood why. Learn what a team of researchers discovered in this classic episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff production of I Heart Radio. Hi
brain Stuff Lauren boge obam here with a classic brain
Stuff episode. As we often discuss on this show, human
bodies are gloriously weird things that science still doesn't entirely understand.
For example, allergies. They're an immune system response that's influenced

(00:23):
by everything from our genes to what we're exposed to
during our first months of life. Today's episode deals with
how even the season it was when you were born
can make a difference. Hey, brain Stuff, Lauren bog obam here,
people born in the fall and winter are more likely
to have allergies than people born in the spring and summer.

(00:44):
While that might be news to you, it certainly was
to me. The scientific community has known about it for years,
and a recent study published in the European Journal of
Allergy and Clinical Immunology set out to discover why it happens.
Many of us have a unique physical identify or maybe
a noticeable birth mark. We also have certain markers on
our DNA that can help determine things like our weight

(01:06):
and height, our mood swings, and even our risk for
some conditions like schizophrenia. The researchers found out that those markers,
called epigenetic marks, can help determine whether we're at risk
for allergies. We spoke with Dr Gabrielle Lockett, lead author
of the study, via email. She said epigenetic marks are
a way to regulate the expression of genes without altering

(01:26):
the underlying DNA sequence. A gene expression is a process
where information stored in our DNA is translated into instructions
for making proteins or other molecules. Lockett, who is a
postdoctoral research fellow in the Faculty of Medicine at England's
University of Southampton, says that researchers have long known that
your birth season, as well as certain environmental exposures like smoking, famine,

(01:50):
or even your social environment, are associated with certain epigenetic
marks and can alter gene expression. They just didn't know why.
She said epigenetic marks were a good candidate for the
connecting mechanism between birth season and allergies because they can
be altered by environmental exposures, can influence gene expression, and
can last many years. Lockett and her team scanned DNA

(02:12):
samples from three hundred and sixty seven eighteen year olds
who were born on the Isle of Wight in England.
They paid particular attention to certain markers called DNA methylation
in the samples. DNA methylation is one type of epigenetic mark.
Methyl groups help cells reproduce normally, and they can literally
turn genes on or off. When your methyl groups are depleted,

(02:33):
bad genes like those that cause cancer are turned on.
Researchers wanted to know whether certain markers could be linked
to the time of year a person was born, and
whether those people experience allergies like xzema or asthma. Lockett said,
we found that yes, DNA methylation at certain places in
the genome is consistently associated with season of birth. We

(02:55):
went on to discover that these birth seasonal epigenetic marks
are associated with gene expression and could potentially provide a
link to allergic disease. Luckett says her team found similar
results when they duplicated the study with a group of
eight year olds from Holland, but the markers were not
present when the team tested a group of newborns. Lackett
says this suggests that epigenetic markers arise after birth or

(03:17):
maybe even as a result of one's environment. The link
between birth month, and allergy risk applies to all kinds
of allergies, Luckett said. For decades, studies have shown that
people born in autumn and winter are at an increased
risk of not only rhinitis hay fever, but also food allergy,
asthma and eczema. She continued, One large Dutch study found

(03:38):
that people born in ottuman winter were at increased risk
of having immune responses to non seasonal allergies such as
egg white and cow's milk, as well as two seasonal
allergies like pollen, cat dog and house dust mighte. This
suggests that season of birth is associated with a person's
risk of allergy in general. The effect is not restricted
to seasonal allergies. So why would your birth month affect

(04:01):
your risk of allergies? Lock It lists some of the theories.
Lower sunlight exposure during autumn and winter might reduce vitamin
D levels, which have a known connection to allergy risk.
Seasonal fluctuations in the levels of certain allergies such as
pollen or house dust mites, or the age at which
baby gets their first rhinovirus hay fever infection more common
in winter, may also contribute to allergic disease risk. Also,

(04:24):
the seasonal availability of different fruits and vegetables eaten by
the pregnant mother could alter the nutrition that baby is
born in different seasons received during important stages of early development.
But of course our bodies are complicated and more research
is needed before we can know for sure. Today's episode

(04:46):
is based on the article marked at birth Your birth month,
allergies and DNA are linked on how stuff works dot com,
written by Nicole bays Moore. Brain Stuff is production of
by Heart Radio in partnership at house stuff work dot
com and it is produced by Tyler Klang. Four more
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