Telogen effluvium after allergic contact dermatitis of the scalp

Objective: After observing 2 cases of acute telogen effluvium induced by allergic contact dermatitis to hair dyes, we decided to evaluate the effects of acute contact dermatitis of the scalp on the hair cycle. Design: Single-center, 6-month study of consecutive patients affected by acute scalp dermatitis. Setting: Department of Dermatology, University of Bologna, Bologna, Italy. Patients: Diagnosis of allergic contact dermatitis of the scalp was confirmed by patch testing. Eight women presenting with acute contact dermatitis of the scalp entered the study. Hair shedding was evaluated monthly for 6 months by pull test and wash test. Increased hair loss was detected in 4 of the 7 patients who completed the study. Hair loss was mild to moderate and appeared 2 to 4 months after the episode of scalp dermatitis. A scalp biopsy specimen from 2 patients confirmed the diagnosis of telogen effluvium. Conclusions: Allergic contact dermatitis of the scalp should be included among the possible causes of telogen effluvium. The pathogenesis of telogen effluvium caused by contact dermatitis is unknown but may be related to cytokine release during the inflammatory process.