Tuesday, January 9, 2018
Food allergy: Update on prevention and tolerance
The rate of food allergies in the United States keeps on rising, but nobody really knows the exact reasons why. In this month’s issue of the Journal of Allergy and Clinical Immunology, Du Toit and colleagues review the literature and focus on the ‘dual allergen’ hypothesis (J Allergy Clin Immunol 2018; 141(1): 30-40). Briefly, they explain that allergic sensitization may occur when there is low-level skin exposure to food allergens, while tolerance is more likely to develop in children to have early exposures to food proteins. The data are mounting from both animal and human observational studies as well as randomized control studies. The most notable has been the LEAP study, which showed that infants aged 4 to 11 months who consumed peanut products at least three times per week until age 60 months were far less likely to develop peanut allergies than infants who had complete avoidance. Only 3.2% in the peanut-eating group developed peanut allergy, compared to 17.2% in the complete avoidance group. The follow-up study, LEAP-On, demonstrated persistence of this tolerance for at least 12 months, even with strict avoidance in non-peanut allergic children. Similarly, the EAT study suggested that lower rates of food allergies with early introduction of allergenic foods in breastfed infants, although conclusions were less clear-cut than in the LEAP study. The results of other studies have been more variable. Regardless, the LEAP and EAT studies show that early introduction of allergenic foods into infant diet is achievable and safe, and does not affect breastfeeding rates as well as later nutrition and growth. However, there are a lot of challenges. Ensuring adherence to dietary recommendations, determining the dosages of food proteins, and powering studies sufficiently to show meaningful differences are challenges that researchers and clinicians face. This has led to the National Institutes of Health’s recommendation for early peanut introduction to prevent peanut allergy. Other countries have also recommended inclusion of potential common food allergens in complementary feeding regimens at around 6 months. With more research, it is possible that we may find more effective ways to help prevent food allergies.