What Is Sodium Hydroxystearate?
Sodium hydroxystearate is the sodium salt of hydroxystearic acid, a fatty acid derivative most often sourced from vegetable oils such as castor or olive. Once the fatty acid is isolated it is reacted with a mild alkaline solution, usually sodium hydroxide, to form the salt we know as sodium hydroxystearate. This conversion turns an oily raw material into a solid that dissolves more easily in water based formulas.
The cosmetic world began using fatty acid salts like sodium hydroxystearate in the mid-20th century when formulators were looking for gentler alternatives to traditional soap. Its ability to create a creamy, stable lather without stripping the skin soon made it a staple in cleansing bars and liquid washes. Today it appears in a wide range of products including facial cleansers, body washes, solid cleansing sticks, shaving creams, shampoo bars and some makeup remover balms. It is also added to deodorant sticks and certain masks where a mild surfactant is needed to help rinse the product away cleanly.
Sodium Hydroxystearate’s Cosmetic Benefits/Uses
In formulas sodium hydroxystearate serves a single key purpose.
Cleansing: As a mild surfactant it lowers the surface tension of water helping it mix with oils and dirt so they can be lifted off the skin or hair and rinsed away easily. This makes the finished product feel gentle while still giving that satisfying clean sensation. The ingredient also contributes to a rich lather and a smoother texture which can improve user experience and encourage thorough cleansing.
Who Can Use Sodium Hydroxystearate
This gentle cleansing agent is generally well tolerated by all skin types including dry, oily, combination and sensitive skin because it has a mild surfactant profile and a near-neutral pH in finished products. Those with very reactive or allergy-prone skin can still use it in most cases, but should stick with formulas that minimize additional fragrances or potential irritants. There are no skin types for which sodium hydroxystearate is outright unsuitable, though people with known sensitivities to fatty acid salts should proceed cautiously.
Sodium hydroxystearate is usually sourced from vegetable oils so it is suitable for vegetarians and vegans. On rare occasions it can be produced from animal-derived fats, so individuals following a strict plant-based lifestyle may want to verify the supplier or choose brands that explicitly label the ingredient as vegetable-derived.
Pregnant or breastfeeding women can typically use products containing sodium hydroxystearate because it stays on the skin surface and is not expected to absorb systemically at meaningful levels. This is not medical advice; anyone who is pregnant or nursing should review any new skincare product with a healthcare professional just to be safe.
The ingredient does not increase photosensitivity, so extra sun precautions beyond standard daily SPF are not required. It is also odorless and non-volatile, which makes it a good option for those sensitive to strong smells.
Potential Side Effects/Adverse Reactions
Reactions to topical sodium hydroxystearate are uncommon and vary from person to person. The list below covers potential side effects though most users will not experience them when the ingredient is properly formulated and used as intended.
- Mild skin irritation
- Temporary redness or tightness, especially on very dry skin
- Contact dermatitis in individuals with a specific allergy to fatty acid salts
- Stinging sensation if applied to broken or compromised skin
If any of these effects occur discontinue use and consult a healthcare professional if symptoms persist or worsen.
Comedogenic Rating
Rating: 1 / 5
Sodium hydroxystearate is highly water soluble and usually appears in rinse off cleansers where it spends minimal time on the skin. Its fatty acid chain is balanced by the sodium salt, so it does not behave like heavier oils that can block pores. Because of this chemistry and its quick rinse profile it earns a low rating of 1.
In practical terms this means the ingredient is generally suitable for people who are prone to acne or breakouts.
As with any surfactant the final product formula matters; heavy butters, waxes or occlusives paired with sodium hydroxystearate could increase the overall pore clogging potential even if the salt itself is low risk.
Summary
Sodium hydroxystearate is mainly a mild cleansing agent that lifts away dirt, oil and makeup by lowering water’s surface tension, then rinses off without stripping the skin. It also improves lather and texture giving products a creamy feel that users enjoy.
While not a headline grabbing ingredient it shows up steadily in bar cleansers, liquid washes, shaving creams and solid deodorants because it is dependable, easy to work with and fits current trends for gentle surfactants and water free formats.
Safety data and decades of use point to a low irritation profile for most skin types, including sensitive skin. Still, everyone’s skin is different so it is smart to perform a quick patch test when trying any new product that contains sodium hydroxystearate.