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Speaker 1: Welcome to brain stuff from how Stuff Works, Hey, brain Stuff,

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Speaker 1: Lauren bog Obam Here, people born in the fall and

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Speaker 1: winter are more likely to have allergies than people born

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Speaker 1: in the spring and summer. While that might be news

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Speaker 1: to you, it certainly was to me. The scientific community

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Speaker 1: has known about it for years, and a recent study

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Speaker 1: published in the European Journal of Allergy and Clinical Immunology

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Speaker 1: set out to discover why it happens. Many of us

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Speaker 1: have a unique physical identifier, maybe a noticeable birth mark.

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Speaker 1: We also have certain markers on our DNA that can

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Speaker 1: help determine things like our weight and height, our mood swings,

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Speaker 1: and even our risk for some conditions like schizophrenia. The

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Speaker 1: researchers found out that those markers, called epigenetic marks, can

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Speaker 1: help determine whether we're at risk for allergies. We spoke

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Speaker 1: with Dr Gabrielle Lockett, lead author of the study, via email.

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Speaker 1: She said epigenetic marks are a way to regulate the

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Speaker 1: expression of genes without altering the underlying DNA sequence. Gene

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Speaker 1: expression is a process where information stored in our DNA

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Speaker 1: is translated into instructions for making proteins or other molecules. Lockett,

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Speaker 1: who is a postdoctoral research fellow in the Faculty of

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Speaker 1: Medicine at England's University of Southampton, says that researchers have

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Speaker 1: long known that your birth season, as well as certain

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Speaker 1: environmental exposures like smoking, famine, or even your social environment,

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Speaker 1: are associated with certain epigenetic marks and can alter gene expression.

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Speaker 1: They just didn't know why. She said. Epigenetic marks were

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Speaker 1: a good candidate for the connecting mechanism between birth season

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Speaker 1: and allergies because they can be altered by environmental exposures,

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Speaker 1: can influence gene expression, and can last many years. Lockett

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Speaker 1: and her team scanned DNA samples from three hundred and

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Speaker 1: sixty seven eighteen year olds who were born on the

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Speaker 1: Isle of Wight in England. They paid particular attention to

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Speaker 1: certain markers called DNA methylation in the samples. DNA methylation

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Speaker 1: is one type of epigenetic mark. Methyl groups help cells

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Speaker 1: reproduce normally, and they can literally turn means on or off.

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Speaker 1: When your methyl groups are depleted, bad genes like those

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Speaker 1: that cause cancer are turned on. Researchers wanted to know

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Speaker 1: whether certain markers could be linked to the time of

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Speaker 1: year a person was born and whether those people experience

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Speaker 1: allergies like eczema or asthma. Luckett said, we found that yes,

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Speaker 1: DNA methylation at certain places in the genome is consistently

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Speaker 1: associated with season of birth. We went on to discover

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Speaker 1: that these birth seasonal epigenetic marks are associated with gene

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Speaker 1: expression and could potentially provide a link to allergic disease.

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Speaker 1: Luckett says her team found similar results when they duplicated

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Speaker 1: the study with a group of eight year olds from Holland,

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Speaker 1: but the markers were not present when the team tested

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Speaker 1: a group of newborns. Luckett says this suggests that epigenetic

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Speaker 1: markers arise after birth or maybe even as a result

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Speaker 1: of one's environment. The link between birth month and allergy

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Speaker 1: risk applies to all kinds of allergies, Luckett said. For decades,

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Speaker 1: studies have shown that people born in autumn and winter

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Speaker 1: are at an increased of not only rhinitis hay fever,

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Speaker 1: but also food allergy, asthma, and eczema. She continued, one

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Speaker 1: large Dutch study found that people born in autumn and

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Speaker 1: winter were at increased risk of having immune responses to

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Speaker 1: non seasonal allergens such as egg white and cow's milk,

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Speaker 1: as well as two seasonal allergens like pollen, cat dog

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Speaker 1: and house dust mite. This suggests that season of birth

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

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Speaker 1: the effect is not restricted to seasonal allergies. So why

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Speaker 1: would your birth month affect your risk of allergies? Locket

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Speaker 1: lists some of the theories. Lower sunlight exposure during autumn

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Speaker 1: and winter might reduce vitamin D levels, which have a

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Speaker 1: known connection to allergy risk. Seasonal fluctuations in the levels

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Speaker 1: of certain allergies such as pollen or house dust mites,

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Speaker 1: or the age at which baby gets their first rhinovirus

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Speaker 1: hay fever infection more common in winter, may also contribute

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Speaker 1: to allergic disease risk. Also, the seasonal availability of different

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Speaker 1: fruits and vegetables eaten by the pregnant mother could alter

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Speaker 1: the nutrition that babies bore in different seasons received during

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Speaker 1: important stages of early development. But of course, our bodies

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Speaker 1: are complicated and more research is needed before we can

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Speaker 1: know for sure. Today's episode was written by Nicole Baysmore

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Speaker 1: and produced by Tyler Clang. For more on this and

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Speaker 1: lots of other remarkable topics, visit our home planet how

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Speaker 1: stuff works dot com,