Immediate rhinoconjunctivitis induced by metamizole and metronidazole

Objective: To report a case of immediate rhinoconjunctivitis induced by both metamizole and metronidazole. Methods: Skin-tests (prick and intradermal) were performed with metamizole, metronidazole, and espyramicine. Standard PAST was carried out with metamizole and metronidazole. Oral challenge tests were performed single blind with Rhodogil, metronidazole, espyramicine, metamizole, aspirin, and propyfenazone. Results: Both skin tests and PAST were negative. We also found that the patient tolerated therapeutic doses of espyramicine, aspirin, and propyfenazone. Challenges with Rhodogil, metamizole, and metronidazole elicited immediate rhinoconjunctivitis. Conclusion: This is an exceptional case of immediate rhinoconjunctivitis induced by two unrelated drugs (metamizole and metronidazole). The pathogenic mechanism implicated in this process remains unclear. Inhibition of the cyclooxygenase pathway was excluded and we could not demonstrate the presence of specific IgE antibodies. Nevertheless, an immunologic or idiosyncratic mechanism could be responsible.