Unusual Lysozyme-induced anaphylaxis in an egg-allergic child

A nine-year-old egg allergic child developed anaphylaxis after ingesting the lysozyme-containing over-the-counter-drug Lysopaine®. He complained of a sore throat without fever or cough. His mother administered him one sublingual tablet of the over-the-counter drug Lysopaine®, containing 20 mg lysozyme hydrochloride. A few minutes after intake of the drug, he developed anaphylaxis and received 300 mg intramuscular epinephrine. HE was not exposed to other allergens. The responsibility of lysozyme was confirmed by positive skin prick tests for Lysopaïne® and the presence of specific IgE against lysozyme. When giving this treatment to her son, his mother had no idea that it could contain egg protein and she did not perceive lysozyme as an allergenic protein. However, the box mentioned the presence of lysozyme and also specified “contains lysozyme extracted from egg”. Lysozyme, a minor egg allergen, may induce anaphylaxis in egg-allergic patients. Lysozyme can be found in many commonly consumed industrial food and drug products and its labelling may be misleading. Our observation highlights the importance of properly educating allergic patients to recognize allergens, even minor ones.