[Effect of histamine on the positive reactions produced during skin tests]

The effect of histamine control on the reaction produced by adjacent allergens or diluent control during skin test was evaluated in 742 patients sensitized to one or more inhalant allergens. In 4 cases (0.7%) both the diluent control and all the tested allergens were positive thus indicating an altered cutaneous reactivity. The allergens placed near the histamine control were positive in 183 cases (24.7%). Among these 144 (19.4%) were strong positive results according to the history. In 39 cases (5.2%) the positive result didn't correlate with the history. Of note in 35 cases (4.7%) the reaction was classified as weak positive (+) according to Berg and Johansson (1974). Although our findings confirm only partially those from Terho and Coworkers, we agree with the Authors on the opportunity of positioning the histamine control at a suitable distance from other allergens during skin test.