(p. 150) The histamine-inhalational test 

It is well known that asthmatics demonstrate an increased reactivity of the bronchial airways to chemical mediators like histamine. . . . Inhalation tests with histamine were introduced by Curry in 1946 and since then have been widely used to study non-specific bronchial reactivity. However, the methods have not been standardized and the results are difficult to interpret. In this paper we use a simple dose-response method to examine the effects of inhaled histamine in normal subjects, well controlled asthmatics, and patients with rhinitis or chronic cough. Histamine-inhalation tests were carried out in 307 adults. . . . Non-specific bronchial reactivity was increased in 3% of presumed normal subjects, in 100% of active asthmatics and in 69% of asymptomatic asthmatics with previous symptoms only at times of exposure to clinically relevant allergens. It was also increased in 47% of patients with cough and no other chest symptoms, in 40% of patients with rhinitis and vague chest symptoms not by themselves diagnostic of asthma, and in 22% of patients with rhinitis and no chest symptoms. . . . The results draw attention to the clinical relevance of increased bronchial reactivity and particularly to the close relationship between the level of increased reactivity and minimum therapy required to maintain good control of asthma.