A left versus right side comparative study of Epiquick patch test results in 100 consecutive patients

4 strips of 5 Epiquick patch tests (19 allergens plus 1 control) were applied symmetrically in duplicate on the left and right sides of the upper back in 100 consecutive patients. 70 positive allergic patch test reactions were recorded on the left side and 67 on the right side. 67 positive reactions were concordant on both sides (64 with the same score of intensity and 3 with a different score). 3 positive reactions (in 2 patients) on the left side were negative on the right side (1 TMTD, 1 cobalt chloride and 1 wool alcohols). At rechallenge 6 weeks later, they were positive. No explanation could be found for negative results at the first challenge on one side and not on the other. The rate of non-reproducible positive results to the overall number of positive reactions was 4.2%. The good reproducibility rate (95.8%) provides useful information for further comparative studies.