Chlorothalonil, a possible cause of erythema dyschromicum perstans (ashy dermatitis)

We studied 39 patients with erythema-dyschromicum-perstans-like dermatitis seen at Changuinola Hospital in Panama. They were compared with 41 controls. The 2 groups were native field workers of the banana plantations exposed to many pesticides. In 34 patients, there was a positive patch test reaction to 2,4,5,6-1,3-tetrachloroisophthalonilnitrile (chlorothalonil, TCPN) 0.001% in acetone. In 39 cases, biopsies showed a lichenoid tissue reaction compatible with a chronic pigmented dermatitis or erythema-dyschromicum-perstans-like dermatitis. Chlorothalonil is possibly the cause of the pigmented dermatitis observed in the 39 banana farm workers studied. Until additional studies are carried out, we consider this a possible rather than definite cause-and-effect relationship.