If you glance at the back of a skincare bottle and spot sodium hydroxide, it is entirely understandable why you might pause. Raw, concentrated sodium hydroxide (chemical formula NaOH)—famously known as lye or caustic soda—is an intensely alkaline compound. Safety data sheets classify it as causing severe skin burns and eye damage, which is why formulators handle it using strict protective gear during production.
However, an ingredient in its raw form behaves very differently from that same ingredient inside a finished product. In skincare, sodium hydroxide is added in minuscule, carefully measured amounts—typically well under 2%. Crucially, it does not remain as sodium hydroxide in the final blend. Instead, it reacts with the acidic components, neutralises itself, and leaves behind water and a mild salt. By the time the product touches your skin, the raw compound has effectively disappeared, leaving behind a balanced, skin-safe formula rather than a caustic chemical.
Benefits for Your Skin
Sodium hydroxide is not an "active" ingredient like retinol or vitamin C—it does not directly brighten, plump, or exfoliate your skin. Instead, its benefits are indirect yet vital to how your products perform.
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It makes exfoliants safe and effective: Key active ingredients like glycolic, mandelic, lactic, and salicylic acids deliver smoother skin and clearer pores, but only within a precise pH window. If a product is too acidic, it damages the skin barrier. Sodium hydroxide acts as a balancing counterweight, allowing formulators to deliver effective acid concentrations at a pH your skin can comfortably tolerate.
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It stabilises the formula: Skincare products can drift in pH over time due to temperature shifts or ingredient interactions. Sodium hydroxide buffers the formula, ensuring your product performs just as reliably in month three as it did during week one.
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It keeps active ingredients active: Acid-based actives require a specific environment to do their job. By maintaining the correct pH, sodium hydroxide ensures that key ingredients continue working effectively throughout the product's shelf life.
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It improves texture and application: Sodium hydroxide influences how thickening agents behave, helping gels and creams glide smoothly across the skin for an even delivery of active ingredients.
The Two Main Functions of Sodium Hydroxide
While its main duty in modern formulations is supporting active ingredients, sodium hydroxide generally serves two primary purposes in cosmetics:
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pH Adjustment: This is its main role. Because skin sits naturally at a slightly acidic pH of roughly 4.5 to 5.5, sodium hydroxide is used to raise acid-heavy formulations to a level that respects the skin's natural barrier.
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Saponification: In traditional soap-making, sodium hydroxide reacts with fats and oils to create soap. In modern foaming cleansers, it can play a minor supporting role in developing texture and lather.
Safety and Guidance
When formulated correctly, sodium hydroxide is safe. Cosmetic safety assessments, including evaluations by the Cosmetic Ingredient Review panel, confirm its safety within regulated limits. Standard guidelines typically cap its use at 0.25% for leave-on formulations and between 2% and 5% for rinse-off products.
The primary precaution involves concentration and product placement. Sodium hydroxide is not intended for use around the delicate eye area, which is why acid-based exfoliants and cleansers should always be kept clear of your eyes.
REFORM Skincare Products Containing Sodium Hydroxide
Because REFORM Skincare focuses heavily on high-performance antioxidants and acids, sodium hydroxide plays an essential supporting role across several of their formulations. Based on the brand's published INCI lists, it appears in the following products:
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Glycolic Acid Foaming Cleanser: Used as a pH adjuster alongside sodium carbonate to buffer the formula, making a potent AHA cleanser suitable for daily use.
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Repair & Renew Gel: Works alongside mandelic, glycolic, and phytic acids to balance this multi-acid exfoliant so it refines skin texture without causing irritation.
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Radiance Renewal Kit: Features the Glycolic Acid Foaming Cleanser as part of its three-step exfoliating routine.
REFORM Skincare publishes full INCI ingredient lists for every product, making it straightforward to check individual items if you wish to review their formulations.
Sodium hydroxide suffers from an unfair reputation based on its raw state. Inside a finished skincare product, it functions as a precise, essential tool that allows potent active ingredients to work effectively while keeping your skin barrier safe.
