It has been reported that 20 to 70 per cent of atopic cases in the dog can be controlled with antihistamines, though the effective antihistamine cannot be predetermined. Combination therapy with essential fatty acids (EFAS) and antihistamines has been shown to be useful in dogs. All of the work published to date has been performed in open studies, without the use of placebo, and in dogs where the aim has been to control pruritus as a symptom rather than that caused specifically by atopy. The aim of this study was to assess the combined effects of four antihistamines; hydroxyzine, chlorpheniramine, cyproheptadine and clemastine; with both an EFA supplement and a placebo of olive oil, in 25 dogs to control pruritus in clinically proven cases of atopy.