Thesodium hydroxide, also known as caustic soda, is used in very small amounts in cosmetic formulas to adjust the pH.
What is "Sodium Hydroxide" and what is its purpose?
- Sodium Hydroxide: What is it?
- Sodium Hydroxide: What is its purpose?
- The current regulations regarding sodium hydroxide
Sodium Hydroxide: What is it?
With the chemical formula NaOH, sodium hydroxide is an inorganic compound. Na+ represents sodium and OH-, the hydroxide ions. Soda is alkaline by nature: its pH is basic, that is to say, greater than 7. It comes in the form of pellets or white crystalline powder that is soluble in water.
Sodium Hydroxide: What is its purpose?
It is crucial that a skincare product does not significantly disrupt the skin's pH, which is slightly acidic. Indeed, when the skin's acid mantle is damaged, it paves the way for irritations and unwanted bacteria. In skincare, sodium hydroxide is therefore used to adjust the pH of certain formulas and thus optimise their skin tolerance. When dissolved, caustic soda reacts with acids. The pH becomes basic as the acids are gradually eliminated.
A second application of sodium hydroxide pertains to the production of soaps. Indeed, lye is one of the reactants in the saponification process; it hydrolyses fats (triglycerides) to create a cleansing solution.
The current regulations regarding sodium hydroxide.
According to the European cosmetic regulations, the maximum amount of sodium hydroxide to be used in cosmetic products is limited as follows:
As a solvent in nail cuticle care products: a maximum of 5%.
In hair straightening products: 2% for general use and 4.5% for professional use.
In all instances, this alkaline agent must be used with caution: it is advisable to avoid any contact with the eyes and to keep any skincare product containing it out of the reach of children.
Note : In a cosmetic product, sodium hydroxide is typically used at around 0.10%. At this concentration, it has absolutely no irritating action. There is no risk if you find this name in your Typology products, it is only there to readjust the pH!
Safety Assessment of Inorganic Hydroxides as Used in Cosmetics. Draft Report for Panel Review (2015).