Delayed skin hypersensitivity in man. The effect of repeated tests with low-dose antigen.

The effects of repeated applications of low doses of antigen on subsequent delayed cutaneous hypersensitivity (DCH) responses induced by the same antigen were evaluated. Fourteen healthy individuals were tested with seven different antigens given intracutaneously with the Multitest system device (Institute Mérieux). The procedure was repeated on four occasions at 2-week intervals. At the first test, 11 and 13 participants displayed DCH to tetanus and tuberculin, respectively. Neither the proportion of responding individuals nor the mean diameter of the reactions was changed in subsequent tests. However, the DCH pattern varied significantly between subjects (p less than 0.001; variance analysis). There was also a significant variation between the test occasion and skin reactivity. It is concluded that repeated applications of low-dose antigen by Multitest do not boost the DCH response. However, because of the low frequency of response to certain antigens and the low reproducibility of the test, the usefulness of this test system to evaluate DCH reactivity is limited.