Relative refractory state for late cutaneous allergic responses.

The late cutaneous allergic response (LCAR) is a usual sequel to the wheal-and-flare (early) response in sufficiently intense cutaneous allergic reactions. Allergic reactions with early and late components were produced in the skin of the forearm by the intracutaneous injection of anti-IgE or allergen. One week later, these sites, which were normal in gross appearance, and separate control sites on the opposite forearm, were injected. At the sites of repeat reactions, the wheal diameter of the early response was the same but the LCAR was considerably smaller than at simultaneously injected control sites. This local relative refractory state for LCAR is immunologically nonspecific in the sense that it was manifest even when the antigen injected the second time had no evident immunologic relationship with the antigen injected initially. The refractory state for LCAR was present at 2 wk after the initial reaction, but it was no longer demonstrable after 3 wk. This local relative refractory state for LCAR may represent an inhibitory control mechanism for allergic reactions in man.