An insecticide (2,2-dichlorovinyl dimethyl phosphate and related compounds) in antiflea dog collars caused primary irritant contact dermatitis in four patients who handled dogs wearing these collars. This dermatitis probably will occur with increased frequency and could be confused with mild poison ivy dermatitis.
Cronce PC, Alden HS. Flea-Collar Dermatitis. JAMA. 1968;206(7):1563-1564. doi:10.1001/jama.1968.03150070101023