Exorphins derived from cow's milk casein elicit pseudo-allergic wheal-and-flare reactions in healthy children

Abstract

Summary Beta-Casomorphin-7 and alpha-casein (90–95) are opioid peptides occurring in cow's milk casein digest products. We investigated the direct histamine releasing properties of these peptides in vivo. Intracutaneous skin tests were performed with-β-casomorphin-7, alpha-casein (90–95) and cow's milk extract in 25 children without any clinical indication of cow's milk allergy or intolerance. Immediate wheal reactions were measured and compared with skin reactions to histamine and codeine. Tests were repeated after pretreatment with 10 mg cetirizine, a H1-antagonist. The opioid peptides induced wheat-and-flare reactions in all children. These were concentration-dependent and similar to those observed with histamine or codeine. Pretreatment with cetirizine inhibited skin reactivity to both opioid peptides. With one exception, no skin reaction to cow's milk was found. Degranulation of skin mast cells was observed in a biopsy specimen taken from the skin area injected with alpha-casein (90–95). Beta-Casomorphin-7 and alpha-casein (90–95) caused pseudo-allergic immediate type reactions, apparently by direct histamine release. This may be of relevance with regard to clinical reactions to cow's milk.