Nicotine Patch 'Turns On' Itchy Feeling Sept. 16, 2009 -- If you've tried to quit smoking using nicotine patches or similar therapies, you might have been left with an itchy feeling.

Such smoking cessation aids commonly cause skin, mouth, and nose irritation. The side effects often prompt patients to stop using the products.

Now researchers have discovered why nicotine, applied to the skin, leaves you with the urge to scratch. Their finding could lead to better therapies to help people stop smoking.

Karel Talavera and colleagues say nicotine turns on a channel in the nervous system that's involved in the sensation of pain and irritation. This channel, called TRPA1, is found in the skin and the lining of the nose and mouth. TRPA1 is considered a "chemosensor" because it senses, or detects, certain chemicals, like nicotine. Their experiments were performed using mice.

Talavera's results challenge the theory that the irritation related to nicotine patches occurs when the chemical stimulates nerve receptors that send pain signals from the skin and lining of the nose and mouth.

Their study also revealed that mice lacking TRPA1 had no irritation when given a nasal version of nicotine.

The study appears in this week's online version of Nature Neuroscience.