Ten laboratory beagles were used to determine whether a 1 per cent hydrocortisone conditioner applied topically for three consecutive days would inhibit IgE-mediated immediate and late-phase reactions induced in their skin. The trial was blinded, controlled with the product's vehicle and designed with a crossover. It consisted of three phases: one period without treatment (control phase) and two periods of treatment with either the active ingredient or the vehicle. Immediate and late-phase reactions were induced by the intradermal injection of rabbit anti-canine IgE polyclonal antibodies. Twenty minutes after the intradermal challenge, the diameter of the wheal, but not the erythematous flares, were significantly reduced after the application of the active product. In contrast, IgE-mediated cutaneous late-phase reactions, evaluated by measurements of dermal thickness and eosinophil counts six hours after challenge and the numbers of dermal CD3-positive T lymphocytes after 24 hours, were not reduced by its application.