Acute allergic contact dermatitis

Discrete and confluent, red, scaly, weepy, crusted papules and plaques. A 25-year-old patient consulted a dermatologist for an acute, eczematous dermatitis on her head, neck, and shoulders. The eruption appeared 5 days after she had black hair dye applied to her hair at the hairdresser. Patch tests were positive for paraphenylenediamine. Paraphenylenediamine is a dark dye used in almost all permanent hair dyes and some semipermanent hair coloring. It is a potent allergen that triggers severe, acute contact dermatitis in sensitized individuals.