Role of bronchial irritant receptors in asthma.

Sulphur dioxide inhaled at low concentration had no detectable effect on forced expiratory volume in one second in non-asthmatic atopic controls, but it induced asthma and increased bronchial reactivity in nine symptomless atopic and non-atopic asthmatic patients. This increased reactivity was inhibited by sodium cromoglycate (SCG) and partly inhibited by atropine. This suggests that SCG, in addition to its ability to stabilise mast cells, may also act on bronchial irritant receptors or directly on smooth muscle in asthmatic patients.