Background: Erythromycin and its salts belong to the larger class of macrolides. Erythromycin is well tolerated. The most common side effects are gastrointestinal distress, nausea, and vomiting, which are dose related. Allergic and pseudoallergic reactions due to macrolide antibiotics are uncommon. Anaphylaxis and acute respiratory distress appear in the literature as case reports.
Methods: We report a 24-year-old man who presented 12 years ago a systemic allergic reaction to penicillin, confirmed by skin tests and detection of specific IgE (RAST). Since then he had tolerated erythromycin on several occasions. Nine months ago, his general practitioner prescribed erythromycin orally as treatment for a respiratory infection. Thirty minutes after taking the first dose, 500 mg, he developed an anaphylactic reaction. The episode subsided with treatment with high dose corticosteroids, antihistamines, and epinephrine. Skin prick tests and intradermal tests were performed with erythromycin at different concentrations. We also measured total IgE and specific IgE to erythromycin by CAP and Phadezym RAST (Pharmacia, Uppsala, Sweden), respectively. We also performed a Prausnitz-Küstner test (PK test), and oral challenge test.
Results: Skin testing to erythromycin was not helpful because of cutaneous hyperreactiviness. No significant levels of specific IgE to erythromycin were detected. The oral challenge and the Prausnitz-Küstner test were positive.
Conclusions: The positive history and oral challenge test suggested an anaphylactic reaction to erythromycin. The positive Prausnitz-Küstner test demonstrated the presence of specific IgE to erythromycin.