Ingredient dictionary
Trisodium Phosphate
Also listed as: Sodium Phosphate Tribasic
A sodium salt of phosphoric acid, used mainly to adjust and hold the pH of a formula. Checked against our library November 6, 2026.
The catch: none for most people; check the full product list if your skin reacts easily.
What Trisodium Phosphate does
- Adjusts product pH
- Keeps acidity or alkalinity steady
- Supports formula stability over time
Trisodium phosphate is made by reacting phosphoric acid with a sodium source, such as sodium hydroxide or sodium carbonate. The result is a sodium salt that dissolves easily in water and makes solutions strongly alkaline. That strong alkalinity is exactly what makes it useful for setting pH, but it is kept to small amounts.
Formulators add it to shift a product's pH into a target range and then keep it there. Because it buffers, it resists small changes in acidity during storage. In a finished cosmetic, it is present in very small quantities, so it does not add noticeable texture, scent or feel to the product. You are unlikely to notice it on your skin.
Good for
Suits formulas that need tight pH control; it works quietly in the background rather than as a headline ingredient.
Be careful if
Nothing in particular for most skin types.
Frequently asked questions
Is trisodium phosphate safe in cosmetics?
At the small levels used in cosmetics, it is generally considered well tolerated. Its main job is pH control. Pure, concentrated forms are strongly alkaline and can irritate, so formulas use only tiny amounts. If your skin is sensitive, patch test any new product first.
What does trisodium phosphate do in a formula?
Its main role is to adjust and hold pH. It works as a buffer, so the product stays at a steady acidity or alkalinity during use and storage. Formulators pick it when they need to bring a mix into a set pH range.