A recent study showed that the relationship of season of birth and allergies. Notably, food allergy and atopic dermatitis (eczema) are more common on among children born during the fall season. Previous studies have shown this relationship in Asia and Europe with mixed results.
“The effect of season of birth on atopic dermatitis and food allergy” was published in the Annals of of Allergy, Asthma and Immunology studied over 16 million births in a 1 year period and followed them from birth to 18 years of age.
The population included 49% male, 34% white, 28% Hispanic, 25% black and 2% Asian.
Seasons of birth were defined as:
- Winter (December to February)
- Spring (March to May)
- Summer (June to August)
- Fall (September to November)
Overall the prevalence of atopic dermatitis was 2.68% and food allergy was 0.27%.
The highest prevalence of food allergy and atopic dermatitis were those less than 3 years of age and fell to the lowest levels for those aged 15 to 18 years.
- Odds of atopic dermatitis were higher among those born in fall then winter and summer. The least was in the spring. There was no effect by race.
- Odds of food allergy were higher among those born in fall, followed by winter and summer compared to the spring. Asian children demonstrated the highest odds of food allergy.
In this large study, it showed that birth during the fall season compared with spring season, is a risk factor for both eczema and food allergy, conferring a 14% to 33% increased risk of food allergy and 6% increased risk of eczema. This increased risk persisted into adolescence for both diseases, suggesting that season-specific exposures may be especially impactful during a window in the first months of infancy.
A leading theory regarding the effect of season of birth is Vitamin D production. However, other data, including a trial of vitamin D supplementation in pregnancy, have not found a protective effect of vitamin D on allergic diseases.
In summary, there is clear evidence that birth during fall season is associated with both food allergy and eczema, with effects stronger for food allergy persisting into adolescence for both diseases.