The cow's milk allergy that wasn't: allergy to supplemental oral lactase enzyme.

Background: Allergy to supplemental lactase is sparsely reported in the literature with only one prior case of anaphylaxis documented [2]. Reactions to this agent can occur following cow's milk ingestion which could lead to an erroneous diagnosis of cow's milk allergy in the absence of another explanation.

Case Presentation: Our patient, a 48-year-old male with eczema, exercise-induced asthma and rhinoconjunctivitis, presented with four episodes of systemic reactions characterized by mucosal swelling and asthma symptoms following ice-cream exposure.