Potassium hydroxide is an inorganic compound with the formula KOH, and is commonly called caustic potash.
Potassium Hydroxide is widely used in soft soap products because of its softness and high levels of solubility; soaps comprised of potassium require less water to liquefy, and can therefore containing higher concentrations of cleaning agents than other liquid soaps that are not potassium-based (Wikipedia).
Potassium Hydroxide is used in the cosmetic and skin care industry as a pH adjuster or bufferer in a wide variety of formulas, including bath products, cleansing products, fragrances, foot powders, hair dyes and colors, makeup, nail products, shampoos, shaving products, depilatories, skin care products, and suntan products, according to CosmeticsInfo.org. It has a unique ability to attract water molecules from its environment, and ultimately dissolve into the water that it had originally absorbed, balancing the formula without creating excess weight or changing the composition.
Potassium Hydroxide is extremely corrosive and can be a hazardous irritant when exposure is at high levels. According to its Material Safety Data Sheet, it “May cause irritation. Prolonged contact may produce discoloration. Potassium hydroxide is corrosive! Contact of skin can cause irritation or severe burns and scarring with greater exposures.” Other studies have shown that it can degrade the natural skin barrier.
However, the Cosmetics Database finds it a low hazard ingredient because of the low levels of concentration found in cosmetic and skin care formulas. It notes cancer, occupational hazard (because it is so volatile and corrosive), organ system toxicity and irritation concerns, and cites studies in which in vitro tests on mammalian cells show positive mutation results and animal studies show skin irritation at very low doses.
The European Union classifies Potassium Hydroxide as toxic or harmful and limits workplace exposure. The severity of the effects caused by Potassium Hydroxide depends on the “concentration, the pH, the length of tissue contact time, and local conditions and skin type,” according to CosmeticsInfo.org. The levels of this ingredient found in skin care products is unlikely to have corrosive or damaging effects.