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.