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What is "Sodium Hydroxide" and what is its purpose?

What is "Sodium Hydroxide" and what is its purpose?

Thesodium hydroxide, also known as caustic soda, is used in very small amounts in cosmetic formulas to adjust the pH.

Sodium Hydroxide: What is it?

With the chemical formula NaOH, sodium hydroxide is an inorganic compound. Na+ represents sodium and OH-, the hydroxide ions. Sodium hydroxide is alkaline by nature: its pH is basic, meaning it is greater than 7. It comes in the form of pellets or a 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 gives way to irritations and unwanted bacteria. In skincare, sodium hydroxide is therefore used to adjust the pH of certain formulas and thus optimize their skin tolerance. When dissolved, caustic soda reacts with acids. The pH becomes basic as the acids are eliminated.

A second use of sodium hydroxide pertains to the production of soaps. Indeed, lye is one of the reactants in the saponification process; it hydrolyzes fats (triglycerides) to form a cleansing solution.

The current regulations regarding sodium hydroxide.

According to the European cosmetic regulation,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 necessary 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% concentration. At this concentration, it has absolutely no irritating action. There's no risk if you find this name in your Typology products, it's only there to readjust the pH!

Source:

  • Safety Assessment of Inorganic Hydroxides as Used in Cosmetics. Draft Report for Panel Review (2015).

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