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Moumoujus

SODIUM HYDROXIDE.

Essential CAS 1310-73-2 / BUFFERING, DENATURANT

Sodium Hydroxide is a strong alkaline compound primarily utilized in precision skincare to adjust and stabilize product pH, ensuring formulations are effective, skin-compatible, and safe for consumer use.

Summary

pH adjuster buffering agent saponification agent

Science

Mechanism of Action

Acting as a potent pH adjuster and buffering agent, Sodium Hydroxide neutralizes excessive acidity in cosmetic formulations. This maintains a stable, skin-compatible pH, crucial for product efficacy and safety. In specific applications like soap manufacturing, it facilitates saponification by reacting with fats and oils. At elevated concentrations, it can induce severe tissue damage through liquefactive necrosis, breaking down cell membranes and proteins.

Research

Clinical Evidence

High confidence
Effective range 0.05–2%
Optimal

0.25%

Key findings

  1. 01 Produced no erythema in human patch tests.
  2. 02 Produced erythema within 0.5 hours in human forearm tests.
  3. 03 Recommended level for leave-on products.
  4. 04 Typically used in skincare, studies suggest safe usage and unlikely to cause irritation or harm when properly formulated.
  5. 05 Mildly irritating in human patch tests; occupational health studies also reported irritation.
  6. 06 Supports safety for leave-on formulations, as per the CIR Expert Panel.
  7. 07 Recommended levels for rinse-off products.
  8. 08 Severely irritating in human patch tests.
  9. 09 Supports safety for rinse-off products, as per the CIR Expert Panel.
  10. 10 Corrosive to skin.

Transparency

Dusting Analysis

Not commonly dusted

Sodium Hydroxide is a critical functional ingredient essential for controlling and stabilizing the pH of cosmetic formulations, thereby ensuring product safety and efficacy, rather than acting as an inactive filler ingredient.

The Formula

Formulation

Solubility
Water
Optimal pH 4.7 – 5.75
0 7 14

Stability

As a strong alkali, Sodium Hydroxide is crucial for adjusting product pH into a stable, skin-safe range, ideally between 4.7 and 5.75 to support the skin's barrier function. While its pure form has a pH of 13, it is precisely formulated in cosmetics only up to pH 11 to minimize irritation risks. Solutions with a pH of 11.5 or greater are considered corrosive.

Conflicts

  • Water (reacts violently, liberates substantial heat)
  • Organic acids
  • Inorganic acids
  • Oxidizing agents (e.g., peroxides)
  • Metals (e.g., aluminum, aluminum alloys, carbon steel)

Safety

Safety Profile

CIR Status
Safe as used
Max tested
2%
Sensitization risk Moderate

The CIR Expert Panel affirms Sodium Hydroxide's safety up to 10% in rinse-off products and 2% in leave-on formulations when precisely formulated to be non-irritating. The SCCS further restricts its use to a maximum of 5% in nail cuticle solvents, 2% for general use hair straighteners, and mandates pH must be below 12.7 for depilatories and below 11 for other applications. The FDA identifies it as Generally Recognized As Safe (GRAS) for cosmetic usage, provided it is used in low, effective concentrations. However, in its pure form or at high concentrations (pH 11.5 or greater), it is a potent irritant and corrosive.

Your Skin

Skin Compatibility

Yes Normal
Yes Dry
Yes Oily
No Sensitive
Irritancy High
Comedogenicity Low

Our Assessment

Verdict

Essential

Sodium Hydroxide is an essential ingredient for ensuring the safety and stability of skincare formulations by precisely controlling pH, thereby optimizing product efficacy and preventing irritation when correctly formulated.

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