 One, immune mothers produce a type of antibody called IgG that is specific to allergens, and this has been linked to a lower risk of allergy in their children. Two, several studies have investigated the mechanisms by which maternal IgG can prevent allergy development, but these are not yet fully understood. Three, to summarize previous research, we review literature on urine models of maternal immunization with allergens and human immune regulation after passive therapy with purified IgG. Four, based on our review, a new hypothesis about the mechanisms involved in inhibiting allergy development is proposed, which could serve as a basis for future therapies to prevent allergies. This article was authored by Jefferson Russo Victor.