Itch | Pain

Monday, September 28, 2009

Itching is defined as an unpleasant cutaneous sensation leading to the desire to scratch. It serves as a physiological self-protective mechanism as do other cutaneous sensations like pain, touch, vibration, cold, and heat to help defend the skin against harmful external agents.

Itching can be evoked in the skin directly by mechanical and heat stimuli or indirectly through chemicals. It may also be generated in the central nervous system independently of peripheral stimulation.

Histamine-evoked itch is transmitted by selective slow-conducting subpopulations of unmyelinated C-polymodal neurons. Chemical itch mediators that can cause itch on C-fibers are histamine, neuropeptides, prostaglandins, serotonin, acetylcholine, or bradykinin.

Targets for therapy against itching can be directed to new receptor systems such as vanilloid, opioid, and cannabinoid receptors on cutaneous sensory nerve fibers that may modulate itch. (Stander S, Steinhoff M, Schmelz M, Weisshaar E, Metze D, Luger T: Neurophysiology of pruritus: cutaneous elicitation of itch.Archives of Dermatology. 139(11):1463-70, 2003 Nov.

Therapy such as massage whether done mechanically or electrically to mobilize tissues locally and improve circulation could also be helpful.