Paederus dermatitis is a peculiar irritant contact dermatitis caused when beetles of the genus Paederus (often called rove beetles) are crushed on the skin, releasing the vesicant pederin. The dermatitis is most frequently seen in regions with a hot, tropical climate.

We describe 123 patients who presented to our dermatology department at a suburban teaching hospital located in Tamilnadu, South India, known for its long, hot summers. Ours was a 1-year prospective study (January 2005 to December 2005).

The peak time of presentation was during April. The mean duration of lesions before presentation was 2.7 days. The neck and arms were the most common sites of involvement. Male patients outnumbered female patients in our study (males 65%, females 35%). The mean age of patients was 23.4 years. Clinically, the most common presentation consisted of linear, geographic, erythematous plaques with a “burnt” appearance. In 61% of patients, more than one lesion was present. Vesicles were seen in 33.3% of patients and pustules in 4.9% of patients. “Kissing lesions” were seen in 1.6% of patients. Periorbital involvement occurred in 4.9% of patients. The majority of patients were students residing in various hostels in our campus, within 1 km of rice fields.

Species identification of the Paederus beetles was not done. In addition, skin biopsy of the lesions was not done and no histopathologic examination was performed.

An outbreak of paederus dermatitis can occur in tropical regions. Awareness of the condition and its clinical features will prevent misdiagnosis. Simple preventive measures can be undertaken based on the behavioral pattern of this nocturnal beetle.