What concentration of Sodium Hydroxide is effective?

Typical effective concentrations of Sodium Hydroxide are Typically below 1% in leave-on skincare (trace amounts for pH adjustment), up to 5% in nail cuticle solvents, up to 2% general / 4.5% professional in hair straighteners (EU Annex III limits).

What skin types is Sodium Hydroxide suitable for?

Sodium Hydroxide is suitable for all skin types, oily, dry, combination, sensitive, acne-prone.

The Skin Formulary

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Researched by Helena DeMaria-Williams

Formula IngredientpH Adjuster

Sodium Hydroxide

Q: Can Sodium Hydroxide cause skin irritation?

Sodium Hydroxide has a low irritation risk. Pure sodium hydroxide is a potent skin irritant and sensitiser at concentrations of 10% or higher. However, in finished cosmetic products it is fully neutralised during formulation and poses minimal irritation risk. EU Annex III restricts its use: pH must not exceed 11 in most cosmetic applications, up to 12.7 in depilatories, and concentration is capped at 2% general / 4.5% professional in hair straighteners and 5% in nail cuticle solvents. In typical leave-on skincare, used amounts are well below 1%.

Q: Is Sodium Hydroxide safe to use during pregnancy?

Sodium Hydroxide is rated "caution" for pregnancy use. Limited specific data is available for topical cosmetic use during pregnancy. The Cosmetic Ingredient Review (CIR) panel considers inorganic hydroxides safe when formulated to be non-irritating. Given that no free sodium hydroxide remains in finished products and typical use levels are below 1%, topical exposure is considered low risk, but specific guidance from a healthcare provider is advisable given limited reproductive safety data (Motherfigure / CIR assessment).

Q: Does Sodium Hydroxide increase sun sensitivity?

Sodium Hydroxide has a no sun sensitivity risk. Sodium hydroxide is a pH adjuster with no photosensitising properties. No sun protection precautions are required based on its presence in a formulation.

INCI: Sodium Hydroxide

Sodium hydroxide (also known as lye or caustic soda) is a highly alkaline inorganic compound used in cosmetics in very small amounts to adjust the pH of formulations. In its pure form it is a potent skin irritant, but it reacts fully with acids during manufacturing — meaning no free sodium hydroxide remains in the finished product. It is particularly important in exfoliant and cleanser formulations where maintaining a precise pH (3–4 for AHAs, 4.5–6 for cleansers) is critical to both safety and efficacy.

What does this do in a formula?

pH balancing, formulation stabilisation, ensures active ingredients work at correct pH, enables effective exfoliants and cleansers

Is Sodium Hydroxide safe? Key considerations

Can Sodium Hydroxide cause irritation?

Low Risk

Pure sodium hydroxide is a potent skin irritant and sensitiser at concentrations of 10% or higher. However, in finished cosmetic products it is fully neutralised during formulation and poses minimal irritation risk. EU Annex III restricts its use: pH must not exceed 11 in most cosmetic applications, up to 12.7 in depilatories, and concentration is capped at 2% general / 4.5% professional in hair straighteners and 5% in nail cuticle solvents. In typical leave-on skincare, used amounts are well below 1%.

Does Sodium Hydroxide increase sun sensitivity?

No Risk

Sodium hydroxide is a pH adjuster with no photosensitising properties. No sun protection precautions are required based on its presence in a formulation.

Is Sodium Hydroxide safe during pregnancy?

Caution

Limited specific data is available for topical cosmetic use during pregnancy. The Cosmetic Ingredient Review (CIR) panel considers inorganic hydroxides safe when formulated to be non-irritating. Given that no free sodium hydroxide remains in finished products and typical use levels are below 1%, topical exposure is considered low risk, but specific guidance from a healthcare provider is advisable given limited reproductive safety data (Motherfigure / CIR assessment).

How does Sodium Hydroxide work?

Individuals with known alkali sensitivity (rare); avoid high-concentration professional-grade products without trained supervision should review the considerations above before use.

Sodium Hydroxide

What does this do in a formula?

Is Sodium Hydroxide safe? Key considerations

Can Sodium Hydroxide cause irritation?

Does Sodium Hydroxide increase sun sensitivity?

Is Sodium Hydroxide safe during pregnancy?

How does Sodium Hydroxide work?

Which products contain Sodium Hydroxide?

Bio-Active Ceramide Moisturiser

Supersize Salicylic Acid Cleanser

360° Skin Clearing Serum

15% Vitamin C + EGF Serum

Milk Cleanser

Salicylic Acid Cleanser

Retinol Serum

PHA Body Water Cream

Succinic Acid Treatment

Glycolic Acid Toner

Brighten-i Eye Cream

Peptide Moisturiser

Retinol Eye Cream

Vitamin B, C and E Moisturiser

Beta Hydroxy Acid (BHA) Serum

PHA Toner

10% Azelaic Acid Serum for Redness Relief

Tranexamic Acid Serum

C-50 Blemish Night Treatment

Gentle Exfoliating Cleanser

Cetaphil Gentle Clear Pimple Patches

Gentle Clear Triple Action Blemish Serum

Gentle Exfoliating Salicylic Acid Cleanser, For Face & Body

Gentle Clear Clarifying Cream Cleanser

Soothing Foam Wash

Multi-Peptide + Copper Peptides 1% Serum

Natural Moisturizing Factors + HA

PHA 5% Exfoliating Lip Serum

Natural Moisturizing Factors + PhytoCeramides

Saccharomyces Ferment 30% Milky Toner

Multi-Peptide + HA Serum

Natural Moisturizing Factors + Beta Glucan

AHA 30% + BHA 2% Peeling Solution

Salicylic Acid 2% Solution

Soothing & Barrier Support Serum

Natural Moisturizing Factors + Inulin Body Lotion

Multi-Antioxidant Radiance Serum

Lactic Acid 5% + HA

Lactic Acid 10% + HA

Aloe 2% + NAG 2% Solution

Mandelic Acid 10% + HA

Rice Lipids + Ectoin Microemulsion