Potassium Stearate

Potassium stearate is a soap/surfactant (fatty acid potassium salt) commonly used in cleansers and shaving products; at functional levels it can raise pH and increase cleansing power, which can disrupt the stratum corneum and sting compromised or eczematous skin. While not a frequent allergen, soap-based surfactants are well known to cause irritant contact dermatitis in reactive individuals, especially with repeated exposure or in leave-on residue situations. Given the predictable barrier-disrupting potential in sensitive-skin routines, I score it as mild rather than gentle. Safety Notes: Potassium stearate is most commonly used as a soap/neutralized fatty acid structurant and emulsifier, and in leave-on creams/lotions it is typically present at low levels (~0.1–2%) to aid texture, lamellar structure, and stability without excessive alkalinity. In rinse-off cleansing products (bar soaps, shaving soaps/creams, and soap-based facial/body cleansers), potassium stearate can be a primary surfactant/soap base and is observed at much higher levels, commonly in the 5–15% range and reaching about 20% in high-soap, high-alkali consumer shaving soaps/cleansers. Very high levels are constrained in leave-on products due to pH/irritation risk and emulsifier balance, so the upper end primarily reflects rinse-off formats.