In vivo and in vitro studies on the residual allergenicity of partially hydrolysed infant formulae

Aim: Because allergen-reduced formulae are widely used in the prevention an d treatment of cow's milk allergy in children and because anaphylactic reac tions have been reported for some hydrolysed formulae, it is of clinical re levance to know about the residual allergenicity of so-called hypoallergeni c formulae. Method: We therefore studied the reactions of 20 children (mean age 1.6 years) with proven cow's milk allergy to a variety of formulae, us ing skin prick test, specific IgE in serum, protein content and RAST inhibi tion. Results: Whereas all but two children with a clinically relevant cow' s milk allergy had a positive skin prick test to cow's milk, some children still showed positive responses to the partially hydrolysed formulae. No ch ild had a positive skin test to the amino acid formula. Specific IgE to the partially hydrolysed whey formula (median 0.28 U/ml) was significantly low er (p < 0.003) than to cow's milk. Specific IgE to the partially hydrolysed whey/casein formula, soy/pork collagen hydrolysate and the amino acid form ula was in a low range (median values 0.19, 0.23 and 0.21 U/ml, respectivel y. While determination of the protein content of the formulae gave no valid information, RAST/EAST inhibition was highest for cow's milk, followed by the partially hydrolysed whey formula, partially hydrolysed whey/casein for mula,soy/pork collagen formula, and the amino acid formula. Conclusion: Ski n prick test and RAST inhibition test are suitable methods for determining the residual allergenicity of hydrolysed infant formulae, while determinati on of protein content using the applied modified Lowry method is not helpfu l.