The pathogenesis of canine atopy has not been established completely. Recent studies have shown that tumour necrosis factor alpha and Interleukin-6 play a role in allergic reactions in humans and mice. Pentoxifylline (PTX) suppresses synthesis of these cytokines and may be a useful therapy for modulating the symptoms of canine atopy. The objectives of this study were to investigate the effects of PTX (10mg kg−1 twice daily for 4 weeks) on clinical signs (erythema and pruritus) and intradermal skin test reactivity in atopic dogs (n = 10). The study was a double-blinded, placebo controlled, crossover clinical trial with a washout period of 2 weeks between treatments. Clinical signs were evaluated and scored by the investigator and owners. During PTX treatment, scores of pruritus and erythema decreased significantly. PTX did not affect intradermal skin test reactivity to house dust mite at 15 min (allergen of reference for this study).