Onycholysis secondary to toluene sulfonamide formaldehyde resin used in a nail hardener mimicking onychomycosis.

Two patients with allergic contact dermatitis to the toluene sulfonamide formaldehyde resin present in nail polish and nail hardener, in whom onycholysis developed, are reported herein. Previously, both patients had been unsuccessfully treated with various antifungal medications. Regrowth of all nails occurred within several months after discontinuance of the offending agents. Results of patch tests to the preparation itself, to the toluene sulfonamide formaldehyde resin, and to formaldehyde confirmed the diagnosis in both patients.