Sodium Hydroxide

The short answer

Sodium hydroxide is a pH adjuster.

On ingredient lists you may see Sodium Hydroxide. Older or more chemistry-heavy sources may call it lye or caustic soda. In skincare, its normal job is not to act like an active ingredient. It helps the finished formula land at the right pH.

That distinction matters because sodium hydroxide as a raw material is harsh. Sodium hydroxide inside a carefully made cleanser, moisturiser, sunscreen, or serum is a different conversation.

What the evidence shows

Cosmetic safety. The Cosmetic Ingredient Review safety assessment on inorganic hydroxides^[1] describes sodium hydroxide and related ingredients as alkaline salts used primarily as pH adjusters in cosmetics. The panel concluded they are safe for current cosmetic use when formulated to be nonirritating, with special caution for high-pH hair straighteners and depilatories.

That is the whole point: context decides the risk.

A drop of raw sodium hydroxide is not the same thing as a pH-adjusted finished formula where the ingredient has done its behind-the-scenes work.

Why pH matters. A 2018 review on skin pH^[2] explains that surface pH affects barrier enzymes, shedding, and microbial balance. Sodium hydroxide will not repair the barrier by itself, but pH control can help a product feel more compatible with skin.

Why a formula might need it

Some ingredients make a formula too acidic or too alkaline at first.

Formulators use pH adjusters to bring the final product into the intended range. You may see sodium hydroxide in:

• cleansers
• moisturisers
• SPF products
• salicylic acid products
• azelaic acid formulas
• gels and serums

Think of it like seasoning a soup at the end. You are not eating a spoonful of salt. You are eating the finished soup after the balance has been corrected.

Is sodium hydroxide bad for skin?

Raw sodium hydroxide can burn skin. That is true, and there is no reason to soften it.

But INCI lists are not raw-material warning labels. They tell you what was used to make the final formula. In many products, sodium hydroxide is present because it helped neutralise or adjust the formula. The finished pH and the full product decide comfort.

For sensitive skin, the useful question is not "Does this contain sodium hydroxide?" The better question is:

• Does the product sting?
• Does it leave the face tight?
• Does redness last after use?
• Is the formula fragrance-free and gentle enough for daily use?
• Does the overall routine keep the skin calm?

If a product feels comfortable and does not leave your skin angry, sodium hydroxide on the ingredient list is usually not a reason to panic.

Where it fits in a routine

You do not use sodium hydroxide as a separate skincare step.

You meet it inside finished formulas, often near ingredients that need pH adjustment, such as citric acid, sodium citrate, salicylic acid, or azelaic acid.

This is exactly the kind of boring formulation detail I like. Nobody buys a cleanser because it contains sodium hydroxide. People keep using a cleanser because the finished product cleans without leaving the face tight and annoyed.

When it will not help

Sodium hydroxide will not:

• clear acne
• fade pigmentation
• calm rosacea by itself
• moisturise dry skin
• exfoliate like an acid treatment
• make a harsh formula gentle on its own

It is support chemistry. Support chemistry should be respected, not turned into a miracle or a scare story.

The practical takeaway

My goal with this guide was to gather the useful science on sodium hydroxide in one place, so you can stop hunting for the next clever fix and focus on a simple, effective routine.

That is also why I made the Danish Skin Care Kit: a calm routine built around documented ingredients, and one that has helped more than 100,000 people with problem skin. If even the smallest question is still nagging you, send me an email at info@danishskincare.com.