Sodium Hydroxide: What Is It, Cosmetic Uses, Benefits & Side Effects

Curious about this ingredient? In this article we're explaining exactly what it is and why it's used within cosmetic formulations.
Updated on: June 30, 2025
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We verify all information on this page using publicly available nomenclature standards from The Personal Care Products Council (PCPC), the European Commission's CosIng database and documentation provided directly by ingredient manufacturers. Our analysis is based on technical data from these sources to ensure accuracy and reliability.

What Is Sodium Hydroxide?

Sodium hydroxide, often referred to as lye or caustic soda, is an inorganic compound made of sodium, oxygen and hydrogen atoms, giving it the chemical formula NaOH. It is a strong alkaline substance widely used to control acidity in many industries, including personal care. Commercially, most sodium hydroxide is produced by the chlor-alkali process, which involves the electrolysis of a saltwater solution to separate chlorine gas, hydrogen gas and a highly purified sodium hydroxide solution. When dried or concentrated it forms white pellets or flakes that readily dissolve in water, generating heat in the process.

The cosmetic story of sodium hydroxide dates back to traditional soap making where wood ash and fats were combined to create cleansing bars. As manufacturing methods improved through the 19th and 20th centuries, the ingredient was adopted as a precise pH adjuster, allowing formulators to keep products stable and skin-friendly. Today you will commonly find sodium hydroxide in facial cleansers, clay masks, chemical exfoliation peels, hair relaxers, depilatory creams, serums, toners and even some nail care solutions where pH balance is critical.

Sodium Hydroxide’s Cosmetic Benefits/Uses

In topical products sodium hydroxide serves two main technical roles that help the overall formula perform its best.

  • Buffering: It adjusts and maintains the pH of a product so the finished formula stays within a skin-appropriate range. A stable pH helps active ingredients like acids, antioxidants or peptides remain effective throughout the product’s shelf life while reducing the risk of irritation that can result from an overly acidic or alkaline blend.
  • Denaturant: It can alter protein structure in certain raw materials, which discourages microbial growth and can improve texture or solubility. By destabilizing proteins that microorganisms might feed on, it offers a subtle support to the overall preservation system of the product.

Who Can Use Sodium Hydroxide

When used at the very low levels typical in finished cosmetics sodium hydroxide is generally considered suitable for all skin types, including oily, combination, normal and dry. Those with sensitive or compromised skin should be mindful that formulas containing high amounts of sodium hydroxide, such as professional hair relaxers or certain peel solutions, can feel harsh or stinging because of the strong alkalinity. If your skin barrier is already irritated you may want to choose milder products where the ingredient sits far down the label list.

The compound itself is made synthetically from saltwater so it contains no animal derived material, making it appropriate for vegans and vegetarians. Keep in mind that overall product vegan status also depends on the other ingredients in the formula and on the brand’s manufacturing practices.

At the concentrations used to fine tune pH in everyday skincare sodium hydroxide is not known to pose special risks to women who are pregnant or breastfeeding. Still, this is not medical advice and anyone who is expecting or nursing should run any skincare product past a qualified healthcare professional to be sure it aligns with their personal situation.

Sodium hydroxide does not increase photosensitivity, so it will not make skin more prone to sunburn. It also does not interfere with most topical actives when kept within its normal buffering range, though extremely high pH can reduce the effectiveness of acidic ingredients like vitamin C.

Potential Side Effects/Adverse Reactions

Responses to topical sodium hydroxide differ from person to person. The effects listed below are possible outcomes when the ingredient is present in significant amounts or when a formula is misused, but most users will not experience them in a properly balanced cosmetic product.

  • Skin irritation – tingling, burning or itching can occur if the pH is too alkaline for skin tolerance
  • Dryness or tightness – high alkalinity can disrupt the skin’s natural acid mantle and reduce moisture
  • Redness and inflammation – visible erythema may appear after prolonged contact with strong solutions
  • Chemical burns – concentrated products such as undiluted lye or professional hair relaxers can cause painful lesions and peeling
  • Eye irritation – accidental splashes may lead to watering, stinging or serious damage if not rinsed promptly
  • Allergic or hypersensitivity reactions – rare but possible, showing as swelling or rash

If you notice any unwanted reaction stop using the product immediately and seek guidance from a healthcare professional.

Comedogenic Rating

Rating: 0/5

Sodium hydroxide is water-soluble, leaves no oily film and is used in tiny amounts strictly to adjust pH, so it has no tendency to block pores. Because it rinses away or is fully neutralised inside the formula, it does not linger on the skin surface where breakouts start.

That makes it acceptable for people who are prone to acne or blackheads.

If a product feels overly drying due to high alkalinity your skin may react by producing more oil, but this is an indirect effect rather than true pore clogging.

Summary

Sodium hydroxide mainly works as a buffering agent and a denaturant. By raising pH it brings an acidic formula into the skin-friendly zone and then keeps it there so actives stay stable. Its protein-altering ability helps limit microbial growth and can improve texture.

The ingredient is a quiet workhorse found in countless cleansers, lotions, masks and hair products, yet it rarely gets spotlighted because its job is behind the scenes rather than skin-transforming on its own.

Used at the very low levels typical in cosmetics it is considered safe for all skin types, with irritation risks showing up only when concentrations climb in professional or DIY products. As with any new skincare item it is wise to patch test first to make sure your individual skin agrees with the full formula.

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