What is Sodium Hydroxide?
Sodium hydroxide (chemical formula NaOH) is a strong alkaline compound, also known as lye or caustic soda. In its raw, concentrated form it is genuinely corrosive — safety data sheets classify it as causing severe skin burns and eye damage, which is why formulators handle it with gloves and eye protection during manufacturing. That fact alone is enough to alarm people when they see it listed on a cosmetic label.
But there is a crucial distinction between an ingredient in its raw state and the same ingredient inside a finished formulation. In skincare, sodium hydroxide is used in extremely small, carefully calculated quantities — typically well under 2% of the total formula — and it does not stay sodium hydroxide once the product is complete. It reacts with the acidic components in the formula and is neutralised, leaving behind water and a mild salt. What remains is not lye; it is a balanced, skin-compatible product.
This is a point of confusion worth clearing up early. The sodium hydroxide on your label is not sitting there caustically waiting to burn you. By the time the product reaches your skin, it has already done its job and effectively disappeared.
The Two Main Jobs Sodium Hydroxide Does
Sodium hydroxide plays two distinct roles in cosmetics, and they are worth separating.
pH adjustment. This is its primary role in most modern skincare. Many of the most effective ingredients — glycolic acid, lactic acid, salicylic acid, vitamin C — are acids. Left unchecked, an acid-heavy formula would sit at a pH far below what skin can comfortably tolerate. Sodium hydroxide acts as an alkaline counterweight, bringing the finished product up to a pH that is both effective for the active ingredient and safe for your skin. Your skin's natural pH sits around 4.5 to 5.5, and well-formulated products are designed to respect that.
Saponification. In soap making, sodium hydroxide reacts with oils and fats to create soap. This is the traditional use of lye, and it is why the ingredient has such a formidable reputation. In a modern foaming cleanser, it may play a smaller supporting role in creating the lather and texture you associate with a satisfying wash.
Benefits for Skin
It is important to be honest here: sodium hydroxide is not an "active" in the way retinol or vitamin C is. It does not directly brighten, plump or exfoliate your skin. Its benefits are indirect — but they are real, and they matter more than most people realise.
It makes acids usable. This is the big one. Glycolic acid, mandelic acid and salicylic acid all deliver genuine results — smoother texture, clearer pores, more even tone — but only within a specific pH window. Too acidic and the product damages the skin barrier rather than helping it. Sodium hydroxide is what allows formulators to deliver a powerful acid at a strength that still respects your skin. Without it, many of the exfoliating products you rely on simply could not exist in a safe, effective form.
It stabilises the formula. A product's pH drifts over time. Ingredients interact, temperature changes, and a formula that starts in the right range can wander out of it. Sodium hydroxide helps buffer the formula, keeping it consistent from the first pump to the last. That means the product performs the same way in month three as it did in week one.
It supports texture and spreadability. Sodium hydroxide affects how thickeners behave in a formula, which influences how a gel or cream spreads across your skin. A product that glides on evenly delivers its actives more uniformly than one that sits in patches.
It keeps actives effective. Acid-based actives are only as good as the environment you put them in. By holding the formula at the correct pH, sodium hydroxide helps ensure the ingredient you paid for is actually working when it reaches your skin.
The overall picture: sodium hydroxide is not there to treat your skin directly. It is there to make sure the ingredients that do treat your skin are able to do so safely and consistently.
Is It Safe?
Yes, when used correctly. Sodium hydroxide is permitted for cosmetic use under strict formulation guidelines, and safety assessments from the Cosmetic Ingredient Review panel confirm it is safe in regulated amounts. Recommended levels sit at around 2% to 5% for rinse-off products and roughly 0.25% for leave-on products.
The relevant caution is about concentration, not presence. Something to note: sodium hydroxide is not suitable for use around the eye area, which is why you should keep acid-based cleansers and exfoliants away from your eyes regardless of what they contain.
REFORM Skincare Products Containing Sodium Hydroxide
REFORM Skincare builds its range around antioxidants and acids — the brand's own stated focus — which is exactly the kind of formulation where sodium hydroxide earns its place. Based on the brand's published ingredient lists, the following products contain sodium hydroxide:
Glycolic Acid Foaming Cleanser — REFORM lists sodium hydroxide openly as a pH adjuster, working alongside sodium carbonate as a buffering agent to hold the formula's pH and stability. This is a textbook example of the ingredient doing its most important job: making a strong AHA cleanser usable on a daily basis.
Repair & Renew Gel — the ingredient list includes sodium hydroxide alongside mandelic acid, glycolic acid and phytic acid. Again, the role is balancing a multi-acid exfoliating formula so the acids perform as intended without overwhelming the skin.
Radiance Renewal Kit — this three-step exfoliating routine includes the Glycolic Acid Foaming Cleanser, so sodium hydroxide is present as part of the kit's formulation.
If you are browsing the wider range and want to know whether a specific product contains it, the ingredient list on each product page will tell you. REFORM publishes full INCI lists rather than hiding behind "and other ingredients", which makes it straightforward to check.
The Bottom Line
Sodium hydroxide has a reputation problem that it does not deserve. Judged on its raw form, it is caustic and dangerous. Judged on its role in a finished skincare product, it is a precise and necessary tool — the ingredient that allows acids to work their magic without wrecking your skin barrier.
If you are using an acid-based cleanser or exfoliant, particularly one from a brand built around acids like REFORM Skincare, sodium hydroxide is very likely part of what makes that product effective. It is not something to fear. It is something to understand.
