Hypoallergenic formulas: are they really hypoallergenic?

Central to the management of cow's milk allergy in infancy is the complete elimination of cow's milk protein from the infant's diet for a variable period of time. The principal part of this approach is to provide nutrition for the child by means of hypoallergenic feeding formulas. Although a number of formulas are indeed marketed as hypoallergenic, it is not known with certainty how hypoallergenic they really are. A variety of ways of testing for hypoallergenicity have been developed, including the use of in vivo and in vitro animal model systems, chemical analyses, and patient studies, which are the ultimate test. The purpose of the present report was to review the various ways of testing sensitizing capacity of infant feeding formulas for the treatment of children with cow's milk allergy. English language articles were selected from PubMed, as were selected abstracts that would have immediate, practical clinical implications. The review focuses on themes related to animal models, chemical analysis, and clinical testing and clinical studies of intolerance to hydrolysates. Sensitizing capacity can be tested first in animal models either by in vivo or in vitro techniques. Although the information gained is valuable for preliminary evaluation, such techniques are intrinsically artificial. Second chemical analyses indicate that absence of larger peptides greater than 1,500 Da provides a critical industrial cutoff point. Third clinical effectiveness in child patients is of paramount importance. The results of the present review demonstrate that extensively hydrolyzed formulas are usually effective, but recently intolerance to hydrolysates has been observed. However, use of amino acid-based formulas free of antigens is highly effective in such infants.