Tussockosis: an outbreak of dermatitis caused by tussock moths in Singapore.

An outbreak of acute pruritic rash occurred in March 1990 among 141 residents of a high-rise public housing estate in Bukit Panjang, Singapore. The typical rash consisted of urticarial lesions distributed over the limbs and trunk. The outbreak was associated with a transient increase in tussock moths in the residential estate following an unusual, short dry spell. The aetiology was established when patch tests with crude moth material produced similar eruptions in 5 out of 7 adult volunteers between 40 min and 12 h. Pharmacological experiments with an aqueous extract of moth hairs in isolated guinea pig ileum elicited a response similar to that induced by histamine.