A procedure has been designed (the chamber-scarification test), which possesses greatly increased sensitivity for assessing the irritancy of topically applied materials. A forearm test site is criss-cross scarified by drawing a 30-gauge needle over the skin with just enough pressure to cleave the epidermis without drawing blood. The test agent is applied in an aluminum chamber once daily for 3 days. The advantages of the method over conventional patch testing are: enhanced capacity to measure mild irritants, reduced time (3 days versus 10 to 21 days), less effort, less cost, less discomfort for the volunteers and greater reproducibility.