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 are discovering in this episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:02):
Welcome to brain stuff from how Stuff Works, 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. 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

(00:24):
set out to discover why it happens. Many of us
have a unique physical identifier, maybe a noticeable birth mark.
We also have certain markers on our DNA that can
help determine things like our weight 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

(00:47):
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 the underlying DNA sequence. Gene
expression is a process where information stored in our DNA
is translated into instructions for making proteins or other molecules. Lockett,

(01:08):
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, 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

(01:29):
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 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

(01:54):
is one type of epigenetic mark. Methyl groups help cells
reproduce normally, and they can literally turn means on or off.
When your methyl groups are depleted, 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 eczema or asthma. Luckett said, we found that yes,

(02:19):
DNA methylation at certain places in the genome is consistently
associated with season of birth. We 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

(02:41):
a group of newborns. Luckett says this suggests that epigenetic
markers arise after birth or 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 of not only rhinitis hay fever,

(03:02):
but also food allergy, asthma, and eczema. She continued, one
large Dutch study found that people born in autumn and
winter were at increased risk of having immune responses to
non seasonal allergens such as egg white and cow's milk,
as well as two seasonal allergens like pollen, cat dog
and house dust mite. This suggests that season of birth
is associated with a person's risk of allergy. In general,

(03:25):
the effect is not restricted to seasonal allergies. So why
would your birth month affect your risk of allergies? Locket
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,

(03:46):
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, the seasonal availability of different
fruits and vegetables eaten by the pregnant mother could alter
the nutrition that babies bore 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

(04:08):
know for sure. Today's episode was written by Nicole Baysmore
and produced by Tyler Clang. For more on this and
lots of other remarkable topics, visit our home planet how
stuff works dot com,