POTASSIUM HYDROXIDE (Potassium hydroxide) – function in cosmetics

A strong base used to adjust pH and make soft soaps.

What it is

Potassium hydroxide is a strong alkali. In formulas it raises pH or neutralises acidic ingredients; in liquid soap making it reacts with oils to form potassium soaps.

Where it is used

Found in liquid soaps, cleansers, shaving creams and gels.

Limits of interpretation

The INCI list shows which ingredients are present, not how much of each. Above 1%, ingredients are listed in descending order of weight; below 1% the order is free.

In the finished product it is normally neutralised; its presence does not mean the product is highly alkaline. Free alkali content is regulated in the EU; see the EU regulation section.

EU regulation

EU · Annex III, entry 15aPotassium or sodium hydroxide

Product type: (a) Nail cuticle solvent (b) Hair straightener (c) pH adjuster for depilatories (d) Other uses as pH adjuster Callosity softener/remover (entry 15d)
Maximum concentration: (a) 5% (b) 2% (General use) and 4.5% (Professional use) Entry 15d: 1,5%
Conditions and warnings: (a) Contains alkali Avoid contact with eyes Can cause blindness Keep out of reach of children (b) 1. Contains alkali Avoid contact with eyes Can cause blindness Keep out of reach of children 2. For professional use only Avoid contact with eyes Can cause blindness (c) Keep out of reach of children Avoid contact with eyes
As of: 3 November 2026 · (EU) 2016/622

POTASSIUM HYDROXIDE

What it is

Where it is used

Limits of interpretation

Functions

EU regulation

Products with this ingredient (350)