The ACVD task force on canine atopic dermatitis (VI): IgE-induced immediate and late-phase reactions, two inflammatory sequences at sites of intradermal allergen injections

Intradermal testing is a common diagnostic procedure used in the evaluation of dogs with suspected atopic dermatitis (AD). To do this, most investigators assess the appearance of wheals that develop at the sites of intradermal allergen injections. However, wheals are rarely seen in dogs with naturally occurring AD. Furthermore, infiltration of inflammatory cells into the injection sites can occur 6–24 h later, a phenomenon known as the late-phase reaction. The histological appearance of these late-phase reactions closely approximates that seen in the natural disease, suggesting that they might be more relevant than the immediate reactions. In this paper, we review the literature on immediate and late-phase reactions and re-assess the evidence for using current intradermal testing procedures as a diagnostic test in dogs.