Highly alkaline ingredient (also known as lye) used in small amounts in cosmetics to modulate the pH of a product. It’s also used as a cleansing agent, most often in pure soaps or soap hybrid products. In higher concentrations, potassium hydroxide can aggravate skin, even if used in rinse-off products.
Reference for this information:
Ullman’s Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim.