How are cleansers tested to ensure they do not damage the skin?

Cleansers are routinely tested prior to commercial release for mildness with the Forearm Controlled Application Technique (FCAT). This human test simulates exaggerated washing to determine if irritation occurs. Usually around 20 subjects are enrolled and the left forearm is moistened with warm (90-100 degree F) tap water. A wash technician wets a piece of soft towel with warm water, then squeezes the towel gently to remove excess water. The moistened towel is rubbed in a circular motion on a wetted test bar for six seconds to generate lather and applied to the test site for 10 seconds. The lather remains on the application area for ninety seconds followed by rinsing with warm tap water for fifteen seconds. The arm is patted dry. Sometimes the procedure is repeated for a total of two washings. The controlled washes are performed twice daily for four days spaced by a minimum of three hours. Cleansing products that produce no irritation with the FCAT are considered suitably mild for market release.