Effects of ipsilateral and contralateral counterirritation on experimentally produced itch in human beings.

The experimental study of itch was reviewed, and an experiment performed to test the effects of ipsilateral and contralateral counterirritation distal to the itching wrist. Each of the 18 subjects served in all experimental conditions, receiving cowage as the itch stimulus and a placebo. Counterirritation consisted of a 10-sec immersion of the fingers into a 2 degrees C water bath. Lateral differences both in response to cowage and to counterirritation were obtained. In general, counterirritation reduced itch significantly more than the control procedure during the treatment period and the first three intervals following treatment. The results of the present experiment suggest a central mechanism attenuating the sensation of itch.