SODIUM HYDROXIDE
Commonly Found In
Overview
Sodium hydroxide (NaOH, lye/caustic soda) is a strong alkali used as a pH adjuster in cosmetics and as the saponification agent in bar soap making. At high concentrations it is caustic and corrosive, but in finished cosmetic products it is neutralized to target pH and poses minimal risk. The EU restricts it under Annex III/15a with pH limits.
Also known as: caustic soda, lye, NaOH, sodium hydrate, soda lye
Key Benefits
No direct skin benefit at cosmetic-use levels; functions as a pH adjuster and denaturant. At high concentrations, NaOH is severely caustic. In finished pH-adjusted formulations, studies suggest minimal risk at neutral-to-mildly-alkaline final pH.
Supporting Research
- β’ CIR Expert Panel β Safety Assessment of NaOH: Safe in cosmetics when formulated to final pH β€11; concentration as adjuster is minimal in finished products
- β’ EU Annex III/15a: Restricts NaOH with product-type specific final pH limits
Skin Compatibility Ratings
Comedogenic Rating
Non-comedogenic; strong base used only as a pH adjuster in the formulation process.
Source: CIR Expert Panel; physicochemical properties
Irritancy Rating
Score applies to concentrated NaOH (3β4 on irritancy scale). At typical use levels in pH-adjusted finished formulations, irritancy is typically score 1. Severely caustic at high concentrations.
Source: CIR Expert Panel; EU Annex III
Typical Use Concentration
Range
0.01β0.5% as pH adjuster
Optimal
Quantity sufficient to achieve target pH
EU restricts by final product pH. Not used at high cosmetic concentrations except in hair relaxers under specific conditions.
Works Well With / Avoid
Works Well With
Avoid Combining
Use With Caution
EU Annex III/15a restricts by final product pH. Used in trace amounts in finished cosmetics; caustic only in concentrated form. Hair relaxers may use higher controlled concentrations.
Commonly Found In
Global Regulation Summary
Overview of current status across major international markets.
Detailed Regional Status
| Region | Status | Max Conc. | Conditions | Source |
|---|---|---|---|---|
| πͺπΊ EU | Banned | - | - | Official β |
| πΊπΈ USA | Allowed | - | - | Official β |
| π―π΅ Japan | Allowed | - | - | Official β |
| π°π· Korea | Unknown | - | - | Official β |
| π¬π§ UK | Restricted | - | Follows EU regulations (III/15a) | Official β |
π Why Regulations Differ
EU Annex III/15a restricts NaOH by final product pH limits (same approach as KOH). Japan and US permit use as pH adjuster without specific NaOH concentration limits. Profile nearly identical to potassium hydroxide; both are strong alkalis regulated via pH controls.
Regulation Analysis
Regional Agreement
Banned in EU but allowed in USA, Japan.
Category Comparison
There are 41 ingredients in the BUFFERING category. 100% are banned in at least one major market.
Strictness Ranking
πΏ Natural Sources
Not found in nature in pure form due to its extreme reactivity. However, sodium compounds are abundant in nature (sea salt, mineral deposits). Historically obtained from natural soda ash.
π How It's Made
Produced by the chlor-alkali process: electrolysis of sodium chloride (salt) brine, which simultaneously produces chlorine gas and sodium hydroxide. About 70 million tonnes produced annually.
π Uses in Cosmetics
Used as a pH adjuster in creams, lotions, and cleansers. Essential saponification agent for bar soap manufacture. EU Annex III restricts final product pH. Used in hair relaxers at controlled concentrations.
π¬ Other Applications
Used in soap and detergent manufacturing, paper pulping, food processing (pretzel crusts, olive curing, cocoa processing), drain cleaning, water treatment, and petroleum refining.
π‘ Fun Facts
- β’ Sodium hydroxide is the 'lye' used in traditional soap-making β a process called saponification that has been used for over 5,000 years
- β’ Pretzels get their distinctive dark, shiny crust from being dipped in a sodium hydroxide solution before baking
- β’ It's used to make lutefisk (traditional Scandinavian dish) by soaking dried cod in lye water for days
Data Sources
- β’ EU Cosmetics Regulation 1223/2009 Annex III entry 15a
- β’ CIR Expert Panel β Safety Assessment of Sodium Hydroxide
Last data verification: 2026-04-16
Related Ingredients
AMMONIUM HYDROXIDE
AMMONIA
CINNAMAL
COAL TAR
DIETHANOLAMINE
EUGENOL
Learn More
Frequently Asked Questions
Why is SODIUM HYDROXIDE banned in the EU but allowed in the US?
The EU follows a precautionary principle, banning SODIUM HYDROXIDE under III/15a due to potential safety concerns. The US FDA has not found sufficient evidence to prohibit its use, allowing it under different safety assessment standards. This reflects differing regulatory philosophies between the two regions.
Why is SODIUM HYDROXIDE banned in the EU but allowed in Japan?
The EU prohibits SODIUM HYDROXIDE (III/15a) based on their strict safety criteria. Japan's Ministry of Health, Labour and Welfare (MHLW) has evaluated the ingredient and permits its use, potentially with different safety data or usage conditions.
What is SODIUM HYDROXIDE used for in cosmetics?
SODIUM HYDROXIDE is primarily used for buffering in cosmetic products. It also serves as denaturant. The ingredient is commonly found in various cosmetic and personal care products.
Which countries regulate SODIUM HYDROXIDE?
SODIUM HYDROXIDE is banned in EU. It has concentration limits or usage restrictions in UK. The ingredient is freely allowed in JP, US.
Are there alternatives to SODIUM HYDROXIDE?
Due to regulatory restrictions on SODIUM HYDROXIDE, cosmetic manufacturers often use alternative ingredients with similar functions. For buffering, alternatives may include other approved ingredients in the same category. Consult product labels for specific formulations, and look for products compliant with your region's regulations.
Disclaimer
The information on this website is for educational and informational purposes only and is not intended as medical advice. While we strive for accuracy based on official government databases, cosmetic regulations change frequently. Always consult with a qualified professional or refer to the latest official regulatory documents for compliance. We are not responsible for any actions taken based on the information provided here.