Capsaicin and menthol in the treatment of itch and pain: recently cloned receptors provide the key.

Topical capsaicin is reported to be an effective treatment for idiopathic intractable pruritus ani. While both capsaicin and menthol application produce a transient perianal burning sensation, only capsaicin relieves itching. Classical observations on functional desensitisation of nociceptors by capsaicin may explain the beneficial effects but the recent discovery of a range of receptors which respond to capsaicin, menthol, and temperature, and their expression in subsets of sensory nerve fibres, provides an exciting prospect towards advancing our understanding and treatment of sensory dysfunction.