Effects of a 1 per cent hydrocortisone conditioner on the prevention of immediate and late-phase reactions in canine skin

Ten laboratory beagles were used to determine whether a 1 per cent hydrocor tisone conditioner applied topically for three consecutive days would inhib it IgE-mediated immediate and late-phase reactions induced in their skin. T he trial was blinded, controlled with the products vehicle and designed wit h a crossover. It consisted of three phases: one period without treatment ( control phase) and two periods of treatment with either the active ingredie nt or the vehicle. Immediate and late-phase reactions were induced by the i ntradermal injection of rabbit anti-canine IgE polyclonal antibodies. Twent y minutes after the intradermal challenge, the diameter of the wheal, but n ot the erythematous flares, were significantly reduced after the applicatio n of the active product. In contrast, IgE-mediated cutaneous late-phase rea ctions, evaluated by measurements of dermal thickness and eosinophil counts six hours after challenge and the numbers of dermal CD3-positive T lymphoc ytes after 24 hours, were not reduced by its application.