Ammonium Hydroxide

Ammonium hydroxide is a strongly alkaline pH adjuster/hair dye component that can be corrosive and is a well-documented eye/skin irritant, with irritation risk rising sharply with concentration and contact time. Even at lower cosmetic-use levels, products relying on it to raise pH (e.g., permanent hair color, depilatories) are associated with burning and barrier disruption, and compromised or eczematous skin is particularly vulnerable. Given its intrinsic alkalinity and clinical irritancy profile, I score it very high for patient safety. Safety Notes: In skincare-adjacent cosmetic products, ammonium hydroxide is most often used as a pH adjuster/alkalizing agent and is typically present at very low levels (around ~0.05–0.3%) in rinse-off cleansers/soaps and some leave-on systems where only small additions are needed to neutralize acidic components. The highest consumer-available levels observed are in strongly alkaline, rinse-off depilatory/bleaching/relaxer-type formulations and certain alkaline peels/masks sold OTC, where ammonium hydroxide can reach about ~1–2% to drive high pH and performance; higher levels are uncommon in OTC facial leave-on products due to irritation and safety constraints.