Dietary strategies for early immune modulation in primary food allergy prevention

Abstract

As the global incidence of food allergies continues to rise, effective primary prevention strategies remain a public health priority. Eczema in early infancy is a major risk factor for IgE-mediated food allergies. Exposure to food allergens via inflamed skin promotes a cascade of allergic immune responses and increases the risk of IgE-mediated food allergies. By contrast, early exposure to food allergens via the gut is likely to induce oral tolerance. Landmark studies have demonstrated a significant reduction in the incidence of egg and peanut allergy in response to the early dietary introduction of food allergens. As a result, early feeding guidelines in countries with a high incidence of food allergies have shifted from recommending prolonged allergen avoidance to a policy of early introduction from around 6 months of age, as part of a diverse complementary diet. Uncertainties remain regarding the optimum timing for the introduction of specific food allergens, as well as the minimum effective frequency and dose. Exclusive breast feeding for around 6 months, and continuation to 2 years, is generally recommended but does not appear to consistently prevent food allergies. Perinatal and intermittent supplementary feeding with cow’s milk-based formula may increase the risk of cow’s milk protein allergy. Maternal food allergen avoidance during pregnancy and lactation is not effective. However, maternal consumption of food allergens during breast feeding appears to increase their preventive effect for the infant in conjunction with the early introduction of allergens into the complementary diet. Data on the dietary supplementation of pregnant women, breastfeeding mothers and infants with vitamin D, omega-3 polyunsaturated fatty acids, prebiotics or probiotics for the purpose of food allergy prevention are insufficient to make firm clinical recommendations. In infants with eczema, a combination of early allergen introduction with regular emollient treatment may have additive preventive effects, but clinical trials have so far had mixed outcomes. Further clinical trials combining dietary strategies with interventions aiming to restore the disrupted skin barrier in infants with eczema may provide new insights into effective food allergy prevention in at-risk populations.