Preventing atopy and allergic disease.

Due to the recent exponential increase in food allergies and atopic disorders, effective allergy prevention has become a public health priority in many developed regions. Important preventive strategies include the promotion of breastfeeding and vaginal deliveries, judicious use of perinatal antibiotics, as well as the avoidance of maternal tobacco smoking. Breastfeeding for at least 6 months and introduction of complementary solids from 4-6 months are generally recommended. Complex oligosaccharides in breast milk support the establishment of bifidobacteria in the neonatal gut which stimulate regulatory T lymphocyte responses and enhance tolerance development. Maternal elimination diets during pregnancy or lactation are not effective in preventing allergies. If exclusive breastfeeding is not possible, (supplemental) feeding with a partially hydrolyzed whey-based formula or extensively hydrolyzed casein-based formula may reduce the risk of cow's milk allergy and atopic dermatitis in infants with a family history of atopy. By contrast, asthma and allergic rhinitis at 4-6 years of age are not prevented by this approach. Soy formula and amino acid-based formula have no proven role in allergy prevention. Perinatal supplementation with probiotics and/or prebiotics may reduce the risk of atopic dermatitis, but no reliable effect on the prevention of food allergy or respiratory allergies has so far been found. A randomized trial on maternal fish oil supplementation during pregnancy found that atopic dermatitis and egg sensitization in the first year of life were significantly reduced, but no preventive effect for food allergies was demonstrated. The role of vitamin D deficiency or excess as a risk factor for food allergy and atopic disorders requires further study.