Antihistamines do not inhibit the flare induced by the intradermal injection of autologous plasma in chronic urticaria patients.

BACKGROUND

There is some evidence suggesting that factors other than autoantibodies to FceRI or IgE and histamine released from mast cells may play a role in skin autoreactivity that characterizes many patients with chronic urticaria (CU) and, possibly, in the pathogenesis of this disease.

OBJECTIVE

The effect of antihistamine treatment on autologous plasma skin test (APST) in patients with CU was assessed.

METHODS

24 patients with CU underwent autologous plasma skin test (APST) as well as SPT with histamine 10 mg/ml while taking antihistamines. In 6 cases the same tests had been carried out also before the start of antihistamine treatment. Plasma levels of D-dimer, prothrombin F 1+2 fragment, and vascular endothelial growth factor (VEGF) were measured in 21 patients.

RESULTS

21/24 (87%) patients showed a large flare on APST while taking antihistamines while the skin reaction to histamine 10 mg/ml was abolished or negligible. Little difference in the autologous plasma-induced flare was seen before and after the start of cetirizine therapy in 6 cases, whereas the drug exerted a marked effect on the histamine SPT as well as on the autologous plasma-induced wheal. The APST-induced flare was not associated with patients' response to antihistamine. Plasma levels of VEGF, prothrombin F 1+2 fragment, and D-dimer were increased in plasmas from 8, 9, and 2 patients, respectively.

CONCLUSIONS

Factors other than histamine are probably involved in the flare following APST in CU; such factors might play a pathogenic role particularly in patients not responding to standard antihistamine treatments.