Immediate and delayed contact hypersensitivity to thiocolchicoside

Abstract

Thiocolchicoside is a muscle relaxant, anti-inflammatory, and analgesic. Administered orally, intramuscularly, or topically, this drug is used in the symptomatic treatment of muscular spasms and rheumatologic disorders. Despite its extensive use, thiocolchicoside is a very rare sensitizer. The case reported here is one of simultaneous contact urticaria and a delayed-type contact allergy to thiocolchicoside. The diagnosis was suggested by the patient’s history and demonstrated by immediate and delayed positive skin test responses. The results of patch tests on intact skin (negative in immediate reading) and open tests (positive only on inflamed skin) may indicate that epicutaneously applied thiocolchicoside can induce an immediate reaction only when a damaged epidermal barrier is present. In contrast, skin integrity does not seem to prevent the appearance of a delayed-type reaction to this drug.