Abstract: Objective To evaluate the serum histamine-releasing activity of patients with chronic urticaria and explore the pathogenesis of chronic urticaria. Methods Sixty-two chronic urticaria patients were studied by using in vivo autologous serum skin test (ASST) and in vitro histamine release assay of human cutaneous mast cells incubated with the patient's sera. Results Twenty-four out of 62 patients showed a wheal response to autologous serum (38.71%). Sera from patients with chronic urticaria released a significantly higher quantity of histamine compared with the control subjects (P<0.01), the percentage of histamine release varied from 3.1% to 79.5% (16.44%±14.26%). Twenty-seven serum samples (43.55%) elicited histamine release higher than 15%. Compared with the ASST negative patients, the positive rate and percentage of histamine release were also elevated in the ASST positive patients (P<0.01). Conclusion Histamine-releasing activity is important in the pathogenesis of chronic urticaria by stimulating or facilitating degranulation of cutaneous mast cells.

Key words: Urticaria, Mast cells, Histamine release, Skin tests