We have little to no idea what causes them, and apparently, even less of an idea of anything that might lead to a cure. The rise in allergies has been attributed to so many things, many of them contradictory: too much of the allergen during pregnancy, not enough of the allergen during pregnancy…introducing allergens too soon, introducing them too late.
Now a new study has come up with a totally new angle on allergies after a study of 6,000 children in Finland. The kids had similar environments, diets, and circumstances. The study found one clear factor that made it more or less likely that the kids would have allergies: the time of year that their moms became pregnant.
The babies at the highest risk were born in the fall, with October and November births topping the list.Babies born in these months had an 11% chance of developing an allergy before age 4. The lowest risk of allergies was found in babies born in the summer: June and July babies had less than half as much risk as the Autumn babies, at only 5%.
The study found that the exact timing of gestation made a difference. Mothers who were in their eleventh week of pregnancy in April or May had the most kids with early allergies. The study’s leaders suggested that these spring months are peak times for certain kinds of pollen which may have triggered some kind of immune reaction, either in the mother and the fetus or in the fetus directly. Different birth months also correlated to an uptick in specific kinds of allergies, as well. 11 weeks of gestation is a significant time in fetal development: that’s when antibodies begin to develop. Allergic reactions are the result of an antibody response.
This study doesn’t do much to help a person prevent a baby from having allergies— I guess if you were able to plan a future pregnancy, you could consider timing it accordingly. But it’s also important to remember that while the difference between the highest and lowest risk of allergies is statistically significant, it’s only actually a 5% increase in risk. So no matter what time of year you’re due, the chances of your baby developing an allergy are still quite small.