Minocycline-Induced Delayed Dermographism With Tolerance to Doxycycline.

Minocycline, a semisynthetic tetracycline, is widely used to treat inflammatory skin diseases such as acne and rosacea. Despite its favorable safety profile, it may cause various adverse effects, including hypersensitivity reactions. We describe the case of a 20-year-old male who developed delayed-onset symptomatic dermographism following oral minocycline treatment (100 mg/day) for acne. One week after starting treatment, the patient developed pruritic, evanescent, linear wheal-like lesions at multiple sites, without angioedema or systemic symptoms. Lesions resolved spontaneously within two weeks of drug withdrawal. An oral challenge test with escalating doses of minocycline, up to a cumulative total of 100 mg initially, showed tolerance; however, symptoms recurred after nine consecutive days at the therapeutic dose, confirming causality. Symptoms resolved following drug discontinuation and a 2-day course of oral cetirizine. To evaluate cross-reactivity, prick and intradermal tests with doxycycline were negative, and a 10-day oral doxycycline challenge was uneventful, indicating no cross-reactivity. Symptomatic dermographism is the most common form of chronic inducible urticaria, but its association with minocycline is rare. The underlying immunopathogenesis remains unclear, potentially involving mast cell activation or superantigen-like effects. This case underscores the importance of prolonged drug rechallenge in identifying rare delayed adverse reactions such as minocycline-induced late-onset symptomatic dermographism and supports the safe use of doxycycline as an alternative.