Sodium Hydroxide



No known benefits

Sodium Hydroxide at a glance

  • Highly alkaline ingredient
  • Used in small amounts in cosmetics (such as in exfoliants and cleansers) to adjust pH
  • Is used in hair and nail products to maintain pH
  • Also known as lye

Sodium Hydroxide description

Sodium hydroxide, also known as lye, is a highly alkaline (also known as “basic”) ingredient used in small amounts in cosmetics to establish and hold the pH of a product in an acidic or alkaline formula. This is seen particularly in products such as cleansers and in leave-on exfoliants, where the product’s pH needs to be held within a very specific range for maximum efficacy (between 3-4 is ideal for acid-based exfoliants, while cleansers are generally pH 4.5-6). Pure sodium hydroxide’s pH level is 13, but in cosmetics, it is only used up to pH 11. Sodium hydroxide is seen in many applications in beauty products, such as nail cuticle solvents and hair straighteners, where it’s used in greater amounts (between 2% and 5% concentrations by weight) than in leave-on skin care products or makeup (for example, some lipsticks contain 0.25% sodium hydroxide). It’s also used as a cleansing and denaturing agent. It’s a significant skin sensitizer in concentrations of 10% or greater.

Sodium Hydroxide references

  • International Journal of Trichology, January-March 2015, pages 2-15
  • Journal of Cosmetic Dermatology, September 2010, Volume 9, Issue 3, pages 174-184
  • Acta dermato-venereologica, March 1995, pages 97-101

Peer-reviewed, substantiated scientific research is used to assess ingredients in this dictionary. Regulations regarding constraints, permitted concentration levels and availability vary by country and region.

Ingredient ratings


Proven and supported by independent studies. Outstanding active ingredient for most skin types or concerns.


Necessary to improve a formula's texture, stability, or penetration.


Generally non-irritating but may have aesthetic, stability, or other issues that limit its usefulness.


There is a likelihood of irritation. Risk increases when combined with other problematic ingredients.


May cause irritation, inflammation, dryness, etc. May offer benefit in some capability but overall, proven to do more harm than good.


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Not rated

We have not yet rated this ingredient because we have not had a chance to review the research on it.