Dietary interventions for primary allergy prevention--what is the evidence?

Allergen exposure in the early postnatal life of an infant with a genetic predisposition for allergy is regarded as at least one essential risk factor for later development of allergic diseases. The most important allergen exposure in early life derives from the early nutrition of the baby. Thus, intervention based on the concept of reducing the allergen load in the diet is one approach for primary allergy prevention in children at risk. This includes breastfeeding, allergen-reduced diet of the pregnant and lactating mother, cow milk protein hydrolysate infant formulas (= hypoallergenic infant formula or HA formulas) and time of introduction of complementary food. Data on breastfeeding regarding allergy prevention are inconsistent: preventive with regard to atopic eczema and cow milk allergy in the first 2 years, but contradictory regarding wheezing beyond the first years of life. Allergen-reduced diet of the pregnant mother is not recommended because there is no evidence for a preventive benefit, but instead for unwanted effects on the child's intrauterine development. Data on a restrictive diet during lactation are also inconsistent. If breastfeeding is insufficient in the first 4-6 months, both partially and extensively hydrolyzed formulas have been successfully used to reduce the risk for atopic eczema, but not for asthma or allergic rhinitis, until school age. However, from the available data it is suggested that the preventive potential of a formula is not only dependent on the degree of hydrolyzation and the protein source, but also from other factors like the process of manufacturing the formula. Recommendations for a certain formula should therefore be based on its proven efficacy in controlled clinical trials. For all healthy children with and without risk for allergy, more recent findings support complementary food introduction in the 5th and 6th months--independent of the kind of milk feeding--according to the nutritional needs and abilities of a baby. Delayed introduction of complementary food beyond the 6th month is no longer recommended.