Pharmacological studies on nonimmunologic contact urticaria in guinea pigs

In the present study we examined the effects of chlorpheniramine and ranitidine, indomethacin, BW755C (an inhibitor of cyclo-oxygenase and lipo-oxygenase enzymes of arachidonic acid metabolism), dexamethasone, and capsaicin on nonimmunologic contact urticaria (NICU) induced in the guinea pig ear by benzoic, acid cinnamic acid, cinnamic aldehyde, methyl nicotinate, diethyl fumarate, or dimethyl sulfoxide. The intensity of edema in the urticarial reaction was quantified by measuring the ear thickness. Antihistamines inhibited reactions to intradermal histamine but not to agents causing NICU. Indomethacin and dexamethasone inhibited reactions to cinnamic acid and cinnamic aldehyde but not to other NICU agents. BW755C and capsaicin had no effect on reactions to any of the NICU agents. Mast cell degranulation during the reaction was not seen in histologic sections. Histamine and capsaicin-sensitive nerves did not seem to be essential for the development of NICU in the guinea pig ear. The details of the inhibitory effects of indomethacin and dexamethasone are not clear, but it seems probable that more than one mechanism is involved in NICU due to different agents.