[Allergy to casein hydrolysate formula. A study of sensitizing allergen]

A six-month old baby, who had been fed for 2 months with casein hydrolysate formula (MA-1) for treatment of milk allergy, developed diarrhea. The baby's RAST score for milk was negative. IgE antibodies to MA-1 but not to MA-1 depleted of lipid (fat-free MA-1), were demonstrated by enzyme-linked immunosorbent assay (ELISA). It was confirmed by the appearance of numerous mast cells and eosinophils in a rectal smear taken after challenge with MA-1 (but not detected after challenge with fat-free MA-1) that some component in the lipid of MA-1 must be an allergen in this patient.