Studies on non-immune immediate contact reactions in an unselected population

Non-immune immediate contact reactions (NIICR) arising from skin contact with a wide range of chemicals have been well described. There is evidence that many, if not all, individuals are susceptible to this effect; it may be just a matter of applying a higher dose to the most resistant types of skin. In this work, we chose to evaluate susceptibility to development of NIICR in a large unselected population. Skin tests were made with 3 known urticants (benzoic acid, trans-cinnamic acid and methyl nicotinate), each at 2 concentrations. In a group of 200 volunteers, it was demonstrated that all 3 chemicals induced NIICR in the majority of people. Approximately 10% of the volunteers appeared particularly sensitive, reacting fairly strongly to 2/3 urticants. In contrast, another subset, also about 10%, failed to respond significantly to any of the chemicals at any dose. However, strong reactivity to one urticant was not predictive of the reaction to the other urticants. In a number of cases, individuals reacting strongly to one urticant reacted very little if at all to the other urticants. Also, the type of response, erythema or oedema, was specific to an individual. There was no significant correlation with age or sex on the degree of NIICR. In conclusion, it has been demonstrated that there is a wide interindividual variation in the response to chemical urticants, which cannot be predicted on the basis of age or sex. The prospect of identifying a panel of individuals generally sensitive to non-immune immediate contact reactions seems limited.