Ingredient glossary
Sodium Hydroxide
On your shelf ✓What Sodium Hydroxide does for your skin, who it suits, and what to watch for.
INCI: Sodium Hydroxide · Also: NaOH, Caustic soda
In short: Sodium Hydroxide delivers pH adjuster, plays a broad, supporting role, and the evidence behind it is strong. One thing to know: introduce it gently.
- What it does
- PH adjuster
- Best for
- A broad, supporting role
- Watch out
- Introduce it gently
- Evidence
- Strong
The Glow take
Nice to have, and nothing to overthink.
Sodium Hydroxide plays a quiet supporting role, rounding out a formula rather than being the reason you buy it.
— Maya
What it does
- pH adjuster
strong evidenceThe CIR Expert Panel's 2016 review of inorganic hydroxides concluded sodium hydroxide is safe as used when formulated to be non irritating, with skin contact…
Why we say this
- The CIR Expert Panel's 2016 review of inorganic hydroxides concluded sodium hydroxide is safe as used when formulated to be non irritating, with skin contact minimised in straighteners and depilatories; it set no percentage ceiling, and the 10 percent leave on and 12.9 percent rinse off figures often quoted from that report are industry reported maximum use levels, not permitted limits.
- In the EU the binding restriction is pH rather than percentage, at pH below 11 for general use as a pH adjuster, and the same report records sodium hydroxide as corrosive in skin tests at concentrations as low as 1 to 5 percent, which is why it is used at trace levels only to neutralise acids.
- CIR safety review Safety Assessment of Inorganic Hydroxides as Used in Cosmetics 2021
On a label: usually effective at 0.01-0.5%.
The inorganic salt family, at a glance
5 inorganic salt entries in the base, Sodium Hydroxide among them. 3 of the 5 are a supporting active.
Who it's for, and who should skip it
Tends to suit
No specific skin type. It is a broadly used ingredient.
Approach with care
- very sensitive
- compromised barrier
- Clogs poresLow
- Irritation riskModerate
How it fits each skin type
- DryNeutral
- CombinationNeutral
- OilyNeutral
- SensitiveTake care
Take extra care if any of these apply to you: compromised barrier.
Where it fits in your routine
What regulators say
In the EU sodium hydroxide is capped at 5% in nail cuticle solvents and 2% in hair straighteners for general use (4.5% professional); elsewhere it is a pH…
What the regulator says, in full
- In the EU sodium hydroxide is capped at 5% in nail cuticle solvents and 2% in hair straighteners for general use (4.5% professional); elsewhere it is a pH adjuster and the product must stay at pH 11 or below, pH 12.7 for depilatories (Annex III entry 15).
Plays well with
- emulsifiers
Sodium Hydroxide, answered
Is Sodium Hydroxide safe during pregnancy?
Yes. Sodium Hydroxide is considered safe to use during pregnancy and breastfeeding. As with anything, if you are unsure it is worth a quick word with your doctor or midwife.
Who should avoid Sodium Hydroxide?
Approach Sodium Hydroxide with care if any of these apply to you: very sensitive and compromised barrier. Its irritation risk is moderate, so introduce it slowly and patch test first.
What concentration of Sodium Hydroxide actually works?
Sodium Hydroxide tends to do its job in the 0.01 to 0.5% range. Much lower and it is likely underdosed.
This, for every label you own
One ingredient is easy. A full label is where it gets confusing. The Ingredient Decoder reads any product and tells you the honest truth, ingredient by ingredient.
Sources & how we reviewed this
- CIR safety review Safety Assessment of Inorganic Hydroxides as Used in Cosmetics 2021summary page only, the document itself was not read