WEBVTT - How Can Your Birth Season Determine Your Allergies?

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<v Speaker 1>Welcome to brain stuff from how Stuff Works, Hey, brain Stuff,

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<v Speaker 1>Lauren bog Obam Here, people born in the fall and

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<v Speaker 1>winter are more likely to have allergies than people born

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<v Speaker 1>in the spring and summer. While that might be news

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<v Speaker 1>to you, it certainly was to me. The scientific community

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<v Speaker 1>has known about it for years, and a recent study

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<v Speaker 1>published in the European Journal of Allergy and Clinical Immunology

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<v Speaker 1>set out to discover why it happens. Many of us

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<v Speaker 1>have a unique physical identifier, maybe a noticeable birth mark.

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<v Speaker 1>We also have certain markers on our DNA that can

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<v Speaker 1>help determine things like our weight and height, our mood swings,

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<v Speaker 1>and even our risk for some conditions like schizophrenia. The

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<v Speaker 1>researchers found out that those markers, called epigenetic marks, can

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<v Speaker 1>help determine whether we're at risk for allergies. We spoke

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<v Speaker 1>with Dr Gabrielle Lockett, lead author of the study, via email.

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<v Speaker 1>She said epigenetic marks are a way to regulate the

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<v Speaker 1>expression of genes without altering the underlying DNA sequence. Gene

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<v Speaker 1>expression is a process where information stored in our DNA

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<v Speaker 1>is translated into instructions for making proteins or other molecules. Lockett,

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<v Speaker 1>who is a postdoctoral research fellow in the Faculty of

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<v Speaker 1>Medicine at England's University of Southampton, says that researchers have

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<v Speaker 1>long known that your birth season, as well as certain

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<v Speaker 1>environmental exposures like smoking, famine, or even your social environment,

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<v Speaker 1>are associated with certain epigenetic marks and can alter gene expression.

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<v Speaker 1>They just didn't know why. She said. Epigenetic marks were

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<v Speaker 1>a good candidate for the connecting mechanism between birth season

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<v Speaker 1>and allergies because they can be altered by environmental exposures,

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<v Speaker 1>can influence gene expression, and can last many years. Lockett

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<v Speaker 1>and her team scanned DNA samples from three hundred and

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<v Speaker 1>sixty seven eighteen year olds who were born on the

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<v Speaker 1>Isle of Wight in England. They paid particular attention to

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<v Speaker 1>certain markers called DNA methylation in the samples. DNA methylation

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<v Speaker 1>is one type of epigenetic mark. Methyl groups help cells

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<v Speaker 1>reproduce normally, and they can literally turn means on or off.

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<v Speaker 1>When your methyl groups are depleted, bad genes like those

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<v Speaker 1>that cause cancer are turned on. Researchers wanted to know

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<v Speaker 1>whether certain markers could be linked to the time of

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<v Speaker 1>year a person was born and whether those people experience

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<v Speaker 1>allergies like eczema or asthma. Luckett said, we found that yes,

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<v Speaker 1>DNA methylation at certain places in the genome is consistently

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<v Speaker 1>associated with season of birth. We went on to discover

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<v Speaker 1>that these birth seasonal epigenetic marks are associated with gene

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<v Speaker 1>expression and could potentially provide a link to allergic disease.

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<v Speaker 1>Luckett says her team found similar results when they duplicated

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<v Speaker 1>the study with a group of eight year olds from Holland,

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<v Speaker 1>but the markers were not present when the team tested

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<v Speaker 1>a group of newborns. Luckett says this suggests that epigenetic

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<v Speaker 1>markers arise after birth or maybe even as a result

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<v Speaker 1>of one's environment. The link between birth month and allergy

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<v Speaker 1>risk applies to all kinds of allergies, Luckett said. For decades,

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<v Speaker 1>studies have shown that people born in autumn and winter

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<v Speaker 1>are at an increased of not only rhinitis hay fever,

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<v Speaker 1>but also food allergy, asthma, and eczema. She continued, one

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<v Speaker 1>large Dutch study found that people born in autumn and

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<v Speaker 1>winter were at increased risk of having immune responses to

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<v Speaker 1>non seasonal allergens such as egg white and cow's milk,

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<v Speaker 1>as well as two seasonal allergens like pollen, cat dog

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<v Speaker 1>and house dust mite. This suggests that season of birth

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<v Speaker 1>is associated with a person's risk of allergy. In general,

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<v Speaker 1>the effect is not restricted to seasonal allergies. So why

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<v Speaker 1>would your birth month affect your risk of allergies? Locket

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<v Speaker 1>lists some of the theories. Lower sunlight exposure during autumn

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<v Speaker 1>and winter might reduce vitamin D levels, which have a

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<v Speaker 1>known connection to allergy risk. Seasonal fluctuations in the levels

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<v Speaker 1>of certain allergies such as pollen or house dust mites,

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<v Speaker 1>or the age at which baby gets their first rhinovirus

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<v Speaker 1>hay fever infection more common in winter, may also contribute

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<v Speaker 1>to allergic disease risk. Also, the seasonal availability of different

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<v Speaker 1>fruits and vegetables eaten by the pregnant mother could alter

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<v Speaker 1>the nutrition that babies bore in different seasons received during

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<v Speaker 1>important stages of early development. But of course, our bodies

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<v Speaker 1>are complicated and more research is needed before we can

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<v Speaker 1>know for sure. Today's episode was written by Nicole Baysmore

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<v Speaker 1>and produced by Tyler Clang. For more on this and

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<v Speaker 1>lots of other remarkable topics, visit our home planet how

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<v Speaker 1>stuff works dot com,