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

This study was designed to test the hypothesis that nedocromil sodium inhibits sensory nerve function to reduce flare and itch in human skin. Nedocromil sodium (2%) or water (control) was introduced into the volar forearm skin of eight non-atopic volunteers by iontophoresis (8 mC) and histamine (20 microl of 1 microM and 300 nM) injected intradermally 10 min later at the same site. 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 scanning laser Doppler imaging at 10 min. The results showed that nedocromil sodium reduced itch scores, totalled over 5 min, by approximately 74.0% (P<0.005) and flare areas by approximately 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 that its mechanism of action is modulation of sensory neurone activation or conduction in the skin.