Effect of local allergen priming on early, late, delayed-phase, and epicutaneous skin reactions.

Allergic disease is reflected in a chronic inflammatory response to an allergen. It is thought that local allergen priming underlies this chronicity. To assess the effect of allergen priming on the amplitude and histologic effect of the allergic reaction, four sequential, intracutaneous skin tests were done with 48-h intervals in 13 patients allergic to the house-dust mite Dermatophagoides pteronyssinus (Dpt). Reactions were measured at 15 min, and at 6, 24, and 48 h. Subsequently, epicutaneous tests were done on Dpt-primed spots (n = 5). At 6, 24, and 48 h, reactions increased after priming (P < 0.006), with unaltered early reactions. Epicutaneous reactions to Dpt on primed spots were larger than in epicutaneous controls on similarly primed skin. Local intradermal priming results in greater inflammatory responses at both intra- and epicutaneous challenge. This mechanism may explain the chronicity of allergic reactions at epithelial surfaces.