Study on the significance of bronchial hyperreactivity in the bronchus obstruction after inhalation of cat dander allergen.

The role of bronchial hyperreactivity in the process that leads to bronchial obstruction after inhalation of an allergen was investigated. In 30 asthmatic children selected because of a positive skin test to cat dander allergen, we measured the histamine threshold, the reaction after allergen inhalation, the allergen-specific IgE concentration in serum, the lowest allergen concentration to which the intracutaneous skin test was positive (skin titer), and the histamine release of leukocytes after challenge with allergen. These variables were correlated with each other. The highest correlation was found between the inhalation reaction and the combination of the histamine threshold and either the allergen-specific IgE or the skin titer. Inhalation was only positive with a decreased histamine threshold (less than or equal to 8 mg/ml). With a low histamine threshold, a positive reaction to inhalation is likely to occur at an allergen-specific IgE concentration of > or = 2 U/ml or at a skin titer of < or = 2.5 x 10(-1) micrograms/ml.