Coincidence of pollen season with the first fetal trimester together with early pet exposure is associated with sensitization to cat and dog allergens in early childhood: A Finnish population-based study.

Coincidence of the first fetal trimester with pollen season strengthens the association between pet exposure and respective sensitization. Pollen exposure at early pregnancy may deviate immune system towards Th2-type reactivity promoting development of specific allergy in case allergen exposure occurred. Therefore, primary prevention of allergic diseases may need to begin during early pregnancy.