Ammonium Hydroxide

Ammonium hydroxide is an alkaline compound formed when ammonia dissolves in water. In skincare, it functions primarily as a buffering agent—helping to neutralise and stabilise the pH of formulations—and as a denaturant, which alters the properties of other ingredients to achieve desired texture or performance characteristics.

It appears in roughly 0.2% of skincare products, typically in very small concentrations. Its role is largely technical rather than therapeutic; it exists to support formula stability and usability rather than to deliver direct skincare benefits.

Ammonium hydroxide works by donating hydroxide ions, which neutralise acids in a formulation and raise pH levels. This buffering action prevents formulas from becoming too acidic or too alkaline, which could compromise both product stability and skin safety.

As a denaturant, it chemically modifies certain ingredients—typically alcohols—to alter their physical properties without destroying their function. This allows formulators to use ingredients in ways that improve texture, spreadability, or sensory experience.

Ammonium hydroxide is a formulation ingredient rather than an active ingredient you need to think about during use. Simply apply products containing it as directed. If you have very sensitive skin or a history of irritation, patch-test any new product first, though irritation from this ingredient at standard cosmetic concentrations would be uncommon.