Histamines, basophils and eosinophils in severe asthma.

1. Arterial and venous whole blood and plasma histamine concentrations and eosinophil and basophil counts were determined in five patients with acute severe asthma who had not previously received steroid therapy, in five who had been maintained on steroid therapy and in a control group of nine patients with acute non-respiratory illnesses. 2. No significant arteriovenous differences were observed for any of these measurements in any of the groups of patients. Significant net loss of arterial histamine does not therefore occur peripherally in acute asthma. 3. When compared with the values for the controls, statistically significant increases were observed, in the group not receiving steroids, for arterial and venous whole blood histamine concentrations, eosinophil counts and basophil counts, and, in those receiving steroids, for the venous basophil counts. 4. When compared with the venous plasma histamine concentration of normal subjects, that of the asthmatic subjects not receiving steroids was significantly raised. 5. The venous plasma histamine concentration of the control group was also significantly higher than that of normal subjects, but less so than in the asthmatic subjects, suggesting that acute illness per se produces an increased plasma histamine concentration.