Comparison of serum histamine-releasing activity and clinical manifestations in chronic idiopathic urticaria.

We found increased serum histamine-releasing activity (HRA) in 27% of patients with chronic idiopathic urticaria. Patterns of clinical manifestations were similar in those with and without serum HRA, including responses to a standard treatment regimen. In HRA+ patients the degree of serum HRA generally correlated with clinical disease activity.