In May 2021, 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 and 1.5 mg cetylpyridinium chloride. A few minutes after intake of the drug, he developed edema of the lips and tongue, associated with dysphonia (Figure 1), without dyspnea, wheezing, urticaria, or vomiting. His mother administered 5 mg of the oral H1-antihistamine mequitazine and 20 min later, he took a 20 mg tablet of prednisolone, because the symptoms persisted, before finally visiting the emergency department. The initial examination showed a breathing rate of 17/min, oxygen saturation of 98% in ambient air, a heart rate of 93 bpm, and a blood pressure of 92/49 mmHg. He showed no wheezing or dyspnea. He was administered another 20 mg tablet of prednisolone and was monitored. Two hours later, he started vomiting and developed abdominal pain, without dyspnea. He was administered 300 mg intramuscular epinephrine (Anapen®) and the symptoms resolved within a few minutes. He was then kept under observation for 8 h and subsequently discharged.
The allergy workup was conducted six weeks later. Skin prick-tests (SPTs) were performed with Lysopaine® and egg white (ALK®). Lysopaine® was crushed and mixed with a physiological saline solution and one drop of the mixture used for prick-testing. Circulating sIgE against lysozyme was measured using the ImmunoCAP System (Phadia, Uppsala, Sweden). Results of the tests, including previous sIgE against egg white and ovomucoid, are shown in Table 1 and Figure 2.