Strong base that acts as a pH adjuster in cosmetics. Added in microdoses to bring the formula acidity to the required level.
Topical application
CWeak evidence. In vitro data, open-label studies, or expert consensus.
In finished cosmetics it only works as a pH adjuster, not an active. After neutralizing acids it converts into a neutral salt.
Sodium Hydroxide (NaOH, caustic soda) is a strong inorganic base. In cosmetics it functions only as a pH adjuster and neutralizer for acidic polymers (carbomer, acrylic copolymers). Concentration in the finished formula is a fraction of a percent. Mechanism. Raises pH to the target range (4.5-6 for most skincare), neutralizes polymer acid groups and converts them to gel form. Without NaOH or its analogues (TEA, AMP, tromethamine) a carbomer serum stays liquid and unstable. Where applied. Gels, serums, cleansers, creams. Often in sunscreens, acid toners (to correct working-solution pH), carbomer emulsions. On the label it appears near the bottom of almost any cream. Evidence base. Safety of a pH adjuster in cosmetics depends on final formula pH, not on NaOH itself. SCCS and CIR confirm safety up to 5% in cleansers and 2% in leave-on. Residual NaOH on skin is fully neutralized. Safety. Concentrated NaOH causes chemical burns, so only manufacturers handle it raw. In the finished product, after neutralization, it is safe and non-irritating. Pregnancy and lactation – safe in finished formulas. Not applied as a standalone agent.
Irritation potential
LowAllergen risk
LowPregnancy
SafeSuitable for
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Sodium Hydroxide is considered safe during pregnancy at typical cosmetic concentrations. Systemic absorption through the skin is minimal.
Sodium Hydroxide suits: oily, dry, sensitive, combination, normal.
Strong base that acts as a pH adjuster in cosmetics.
The INCI name is Sodium Hydroxide. It may also appear as: Гидроксид натрия, NaOH, Caustic Soda.
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