Delayed hypersensitivity reaction to intralesional triamcinolone acetonide following treatment for alopecia areata. Intradermal testing.

BACKGROUND Hypersensitivity reactions to intralesional corticosteroids are very rare and have been infrequently reported. Patch testing is considered the gold standard for diagnosing contact allergic dermatitis. However, intradermal testing is thought to be more accurate and sensitive in selected cases. MAIN OBSERVATION We describe a case of a delayed hypersensitivity reaction to intralesional triamcinolone acetonide following the treatment of alopecia areata. Patch testing to triamcinolone was negative but intradermal testing with a small volume of the same reagent elicited a strong reaction. CONCLUSIONS Patch testingmay be unsuccessful in detecting delayed reactions to intralesional corticosteroids. In such cases intradermal testing at a non-cosmetically sensitive sitemay be a useful diagnostic tool.