Relationship between airways response to allergens and nonspecific bronchial reactivity.

Bronchial inhalation challenges to histamine, methacholine, and at least one antigen were performed on 183 asthmatic patients who previously had received skin tests to at least 16 different antigens. Individuals with a positive skin test and a positive antigen inhalation challenge to the same antigen had lower thresholds of response to both histamine and methacholine. This pattern was statistically significant for mixed trees, mixed grasses, mixed molds, and house dust but not for mixed ragweed. For those individuals who had a negative antigen inhalation challenge, skin test reactivity (positive or negative) alone was not associated with a different threshold of response to histamine or methacholine. Also, a higher percentage of positive antigen inhalation challenges were seen in the group of individuals with a low threshold of response to both histamine and methacholine than in groups with either a moderate or high threshold of response to these chemical agents. The results imply that at least two factors are associated with a positive bronchial inhalation challenge to a specific antigen: nonspecific airways hyperreactivity, as indexed by a methacholine or histamine inhalation challenge, and a positive skin test.