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
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 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, 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 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
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, 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 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,
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, 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, 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 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,