Season you were born in affects allergy risk

Winter. Spring. Summer. Fall. Which season were you born in? As it turns out, the season in which a child is born can determine whether or not they are more likely to suffer from an allergy in later life.

Researchers at the University of Southampton have discovered specific markers on DNA that link the season of birth to risk of allergy in later life.

The study conducted epigenetic scanning on DNA samples from a group of people born on the Isle of Wight. They found that particular epigenetic marks (specifically, DNA methylation) were associated with season of birth and still present 18 years later.

The research team was also able to link these birth season epigenetic marks to allergic disease, for example people born in autumn had an increased risk of eczema compared to those born in spring. The results were validated in a cohort of Dutch children.

One of the study's authors John Holloway commented, "These are really interesting results. We know that season of birth has an effect on people throughout their lives. However, until now, we did not know how the effects can be so long lasting."

"Epigenetic marks are attached onto DNA, and can influence gene expression for years, maybe even into the next generation. Our study has linked specific epigenetic marks with season of birth and risk of allergy. However, while these results have clinical implications in mediating against allergy risk, we are not advising altering pregnancy timing."

First author Dr Gabrielle Lockett added: "It might sound like a horoscope by the seasons, but now we have scientific evidence for how that horoscope could work. Because season of birth influences so many things, the epigenetic marks discovered in this study could also potentially be the mechanism for other seasonally influenced diseases and traits too, not just allergy."

The team said that further research is needed to understand what it is about the different seasons of the year that leads to altered disease risk, and whether specific differences in the seasons including temperature, sunlight levels and diets play a part. More study is also needed on the relationship between DNA methylation and allergic disease, and whether other environmental exposures also alter the epigenome, with potential disease implications.

The study is published in the journal Allergy.