A cleanser is a substance used to remove dirt, oil, makeup, or other unwanted materials from something, most commonly from skin. You might use a facial cleanser each morning and night to wash away the day's grime, keeping your face fresh and healthy. Unlike harsh soaps that can dry out skin, cleansers are formulated to clean gently while maintaining the skin's natural balance.

The word also applies to products that clean other things. A household cleanser might remove stains from countertops or floors. A drain cleanser breaks down clogs in pipes. What makes something a cleanser rather than just “soap” is often its specialized purpose: it's designed specifically for the job it does.

Think of a cleanser as a cleaning agent: something that actively works to lift away unwanted substances. When someone uses a makeup remover before bed, they're using a cleanser designed for that exact task. When you wash your hands with a gentle foam, you're using a hand cleanser. The word emphasizes the action of cleansing, making something clean and pure again.