Aim: Because allergen-reduced formulae are widely used in the prevention and treatment of cow's milk allergy in children and because anaphylactic reactions have been reported for some hydrolysed formulae, it is of clinical relevance to know about the residual allergenicity of so-called hypoallergenic 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, using skin prick test, specific IgE in serum, protein content and RAST inhibition.
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 child 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 lower (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 formula was in a low range (median values 0.19, 0.23 and 0.21 U/ml, respectively). 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 formula, soy/pork collagen formula, and the amino acid formula.
Conclusion: Skin prick test and RAST inhibition test are suitable methods for determining the residual allergenicity of hydrolysed infant formulae, while determination of protein content using the applied modified Lowry method is not helpful.