Preventing Atopic Diseases During Childhood - Early Exposure Matters

Abstract

Atopic diseases in childhood are a major burden worldwide and there is still a lack of knowledge about treatable causes. In industrialized countries such as Germany, almost every second child is sensitized to at least one common allergen. Recent studies show that although the predisposition to allergies is inherited, the adaptive immune system of neonates and infants follows a developmental trajectory and whether an allergy actually occurs depends also on timing of allergen exposure including diet as well as environmental factors. New recommendations are far from being rigid of allergen avoidance; it is rather moving toward conditions that stand for more biodiversity. The observation that introduction of peanuts or eggs early in life significantly reduced the development of a later allergy will change our recommendations for the introduction of complementary foods. This is consistent with the hygiene hypothesis that early provocation shapes the developing immune system so that it reacts appropriately. Therefore, promoting the development of tolerance is at the heart of sensible allergy prevention - and this begins with the last trimester of pregnancy. In light of this concept, actual recommendations are discussed.

Keywords: Th2 cells; allergen; allergy prevention; atopic disease; children; early exposure; immune tolerance; regulatory T cells.

Figure 1

Primary prevention of allergic diseases (asthma, hay fever, atopic dermatitis). Contact to allergens (milk, peanut, fish, house dust mite) and microbes during pregnancy and early life leads to an active training of the immune system and, therefore, induces active immune tolerance. Thereby, allergy mediating T helper cell of type 2 (Th2)-answers are prevented and tolerance mediating regulatory T cells and Th1 cells dominate. Recommendations for primary allergy prevention during pregnancy and childhood. In orange shows recommendations for allergen avoidance in at–risk children, red boxes recommendations for avoidance of risk factors. Symbols are from smart servier medical art 2020 (https://smart.servier.com/). mo, month.