Late-phase reactions to intradermal testing with Dermatophagoides farinae in healthy dogs and dogs with house dust mite-induced atopic dermatitis.

OBJECTIVE

To determine the prevalence of late-phase reactions to intradermal testing with Dermatophagoides farinae in healthy dogs and dogs with atopic dermatitis and an immediate reaction to D farinae.

ANIMALS

6 healthy dogs and 20 dogs with atopic dermatitis and immediate reactions to D farinae.

PROCEDURE

ntradermal tests were performed with D farinae at 1:1,000 wt/vol and 1:50,000 wt/vol concentrations, and skin reactivity was evaluated after 0.25, 6, and 24 hours. Serum D farinae-specific IgE antibodies were assayed. Extent of lesions (atopy index) and pruritus (visual analogue scale) were evaluated in dogs with atopic dermatitis.

RESULTS

Late-phase reactions were observed in healthy dogs at 6 hours (n = 2 dogs) and 24 hours (1) with the 1:1,000 wt/vol concentration, and at 6 hours (1) and 24 hours (1) with the 1:50,000 wt/vol concentration of allergen. Late-phase reactions in healthy dogs were only observed in dogs with an immediate reaction to D farinae. Late-phase reactions were observed in 11 of 20 dogs with atopic dermatitis at 6 and 24 hours with the 1:1,000 wt/vol concentration and in 10 of 20 at 6 and 24 hours with the 1:50,000 wt/vol concentration of allergen. There was no difference in mean atopy index, mean visual analogue scale of pruritus, or mean serum D farinae-specific IgE concentration of dogs with a late-phase reaction, compared to dogs without a late-phase reaction.

CONCLUSIONS AND CLINICAL RELEVANCE

Late-phase reactions may be observed after an immediate reaction to intradermal skin testing in healthy and allergic dogs but are more commonly observed in dogs with atopic dermatitis.