Ingredient dictionary

Sodium Hydroxide

Also listed as: Caustic Soda, Lye

Sodium hydroxide is a strong alkali, also called caustic soda. In small amounts it adjusts a product's pH, which measures how acidic or alkaline it is. It is on the label of 404 products in our library. Checked against our library November 6, 2026.

The catch: none for most people; check the full product list if your skin reacts easily.

What Sodium Hydroxide does

Raises pH in cleansers and creams
Neutralizes acidic ingredients in formulas
Helps activate certain gel thickeners

Sodium hydroxide is made in large industrial plants, mostly by running electricity through salt water. Its raw form is strongly alkaline and must be handled with care, so formulators add it in very small, carefully measured amounts.

In a finished product, it is there to fine-tune pH, so the formula stays stable and comfortable on skin and hair. It also neutralizes some thickeners, such as certain gel polymers, so they can build a smooth gel or cream texture. In the final product it leaves little feel of its own.

Good for

Good for anyone using everyday cleansers, shampoos or moisturizers, since it helps keep those formulas at a comfortable pH.

Be careful if

Nothing in particular for most skin types.

Frequently asked questions

Is sodium hydroxide safe in skincare?

At the low levels used in finished skincare, it is generally well tolerated. The raw ingredient is strongly alkaline, but manufacturers measure it carefully, and it is used only to bring the product's pH into a comfortable range.

Why is sodium hydroxide in shampoo?

In shampoo it is mainly there to keep the pH in a comfortable range. This helps the cleanser stay stable and suits hair and scalp. Only small amounts are needed.