Data from a Swedish birth cohort study of 2,423 children, published in the American Journal of Clinical Nutrition (Dec 2009;90:1693–1698), found an association between early-life multivitamin supplementation and a reduced risk of allergies.

While the study did not show a benefit for current multivitamin use, it did show that children who took a multivitamin before age four had a lower likelihood of developing allergies later on. The authors suggest that nutritional status during early immune-system development may influence allergy risk, though more research is needed to understand the mechanism.