Ingredient review
Sodium Hydroxide
INCI: Sodium Hydroxide
Sodium hydroxide is a safe pH adjuster in tiny amounts, but it can be irritating if not properly neutralized in the formula.
In plain English
Sodium hydroxide is a strong chemical that can burn skin in its raw form. In skincare, it's used in very small amounts to balance the pH of products like cleansers and soaps. By the time you use the product, it has reacted with other ingredients and is no longer caustic, so it's safe for most people.
Review score
Safety, usefulness, and evidence
Potentially useful with some tradeoffs
The evidence base is relatively strong for its common cosmetic role.
Main practical flags: irritation is high; clogging risk is low.
- Source
- synthetic
- Evidence
- strong
- Irritation
- high
- Clogging risk
- low
Quick decision guide
Useful, but context matters
Sodium Hydroxide can be useful, but watch for high irritation potential.
Plain-English read
Treat this as a practical screening step before you compare products that contain this ingredient.
- Step 1Start with the score, then check the irritation and clogging risk before judging Sodium Hydroxide.
- Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
- Step 3If a product stings, breaks you out, or worsens irritation, judge the finished formula and stop using it even if the ingredient scores well.
Score terms in plain English
Irritation risk
highMore likely to cause dryness, stinging, peeling, or reactivity if used too aggressively.
Clogging risk
lowLess likely to feel heavy or contribute to clogged pores for most skin types.
Evidence level
strongThere is a stronger practical or research basis for the ingredient role described here.
What it is
Sodium hydroxide is an inorganic compound, also known as lye or caustic soda. It is a strong base that is highly alkaline and corrosive in concentrated form. In cosmetics, it is used as a pH adjuster or to saponify oils into soap.
How it works
In skincare formulations, sodium hydroxide is added to raise the pH of a product to a desired level, often to make it less acidic. In soap making, it reacts with fats and oils in a process called saponification, turning them into soap and glycerin. After the reaction, no free sodium hydroxide remains in the final product.
Pros
Effective pH balancer
Sodium hydroxide precisely adjusts the pH of skincare products, ensuring they are gentle on the skin's natural acid mantle.
Essential for soap making
It is the key ingredient in traditional soap production, creating a solid bar that effectively cleanses without stripping the skin when properly formulated.
Cons and cautions
Corrosive in raw form
Undiluted sodium hydroxide can cause severe chemical burns, so it must be handled with extreme care during manufacturing.
Potential for irritation
If a product is not properly formulated, residual sodium hydroxide can irritate the skin, especially for those with sensitive skin.
Best for
- People using properly formulated cleansers and soaps
- Anyone who wants a product with a balanced pH for gentle cleansing
Use caution if
- Individuals with very sensitive or compromised skin should avoid high-pH soaps that may still contain traces of alkali
Usage tips
Safety summary
Sodium hydroxide is safe in finished cosmetic products when used at low concentrations and properly neutralized. The main risk is during manufacturing, not for the end user.
Research notes
Numerous studies confirm that sodium hydroxide is safe in cosmetics at regulated levels. The Cosmetic Ingredient Review (CIR) panel has deemed it safe for use in rinse-off and leave-on products at concentrations up to 2% and 0.5%, respectively.
Common label clues
- Typical concentration
- Less than 1% in leave-on products; up to 2% in rinse-off products
- Regulatory status
- Approved for use in cosmetics by the FDA and EU CosIng database, with concentration limits to ensure safety.
- Common uses
- Cleansers, Soaps, pH-balanced formulations
- Environmental note
- Sodium hydroxide is produced industrially and can be harmful to aquatic life if released in large quantities, but its use in cosmetics is minimal and well-controlled.
Good to know
- Sodium hydroxide is not listed as an active ingredient in finished products because it is consumed in chemical reactions.
- In the EU, sodium hydroxide is regulated and allowed in cosmetics up to certain concentration limits depending on the product type.
Common questions
What is Sodium Hydroxide in beauty products?
Sodium hydroxide is a strong chemical that can burn skin in its raw form. In skincare, it's used in very small amounts to balance the pH of products like cleansers and soaps. By the time you use the product, it has reacted with other ingredients and is no longer caustic, so it's safe for most people.
What does Sodium Hydroxide do in a beauty product?
In skincare formulations, sodium hydroxide is added to raise the pH of a product to a desired level, often to make it less acidic. In soap making, it reacts with fats and oils in a process called saponification, turning them into soap and glycerin. After the reaction, no free sodium hydroxide remains in the final product.
Is Sodium Hydroxide safe for most people?
Sodium hydroxide is safe in finished cosmetic products when used at low concentrations and properly neutralized. The main risk is during manufacturing, not for the end user.
Who should be careful with Sodium Hydroxide?
Individuals with very sensitive or compromised skin should avoid high-pH soaps that may still contain traces of alkali
Research sources
Ingredient reviews are educational and are not medical advice. Patch test new products and ask a licensed clinician about persistent irritation, allergies, pregnancy-specific questions, or diagnosed skin conditions.