Nedocromil sodium inhibits histamine-induced itch and flare in human skin

This study was designed to test the hypothesis that nedocromil sodium inhib its sensory nerve function to reduce flare and itch in human skin. Nedocrom il sodium (2%) or water (control) was introduced into the volar forearm ski n of eight non-atopic volunteers by iontophoresis (8 mC) and histamine (20 mul of 1 muM and 300 nM) injected intradermally 10 min later at the same si te. Itch was assessed on a visual analogue scale every 20 s for 5 min. Weal and flare areas and mean blood flux within the flare were assessed by scan ning laser Doppler imaging at 10 min. The results showed that nedocromil so dium reduced itch scores, totalled over 5 min, by similar to 74.0% (P<0.005 ) and flare areas by <similar to>65% (P<0.03). Neither weal areas nor blood flux within were reduced. These data demonstrate that nedocromil sodium is effective in reducing neurogenic itch and flare in the skin. We suggest th at its mechanism of action is modulation of sensory neurone activation or c onduction in the skin.