What Is Hydroxystearic Acid?
Hydroxystearic acid, also written as 12-hydroxystearic acid, is a fatty acid most often sourced from castor oil. When castor oil is hydrogenated and then split apart, one of the resulting components is this waxy, off-white solid. Chemically, it is stearic acid with an added hydroxyl group at the 12th carbon, a small tweak that changes how it behaves in formulas.
The ingredient first gained attention in the early 1900s for use in industrial lubricants because its thickening power was hard to beat. As cosmetic chemists looked for plant-based alternatives to animal fats, they found that hydroxystearic acid brought structure and a smooth feel to creams and lotions without a greasy aftertouch. Over time, improvements in refining methods made it easy to produce cosmetic-grade material, and today it is a common workhorse in skin care and personal wash products.
Most commercial supply starts with harvested castor seeds. The oil is extracted, hydrogenated to make it more stable, then hydrolyzed to break the triglycerides into their individual fatty acids. After purification, the hydroxystearic acid portion is separated out as flakes, powder or pellets ready for blending.
You will typically spot it in facial cleansers, cream cleansers, clay or cream masks, lightweight moisturizers, body lotions, sunscreen emulsions and even some color cosmetics where it helps keep pigments evenly dispersed.
Hydroxystearic Acid’s Cosmetic Benefits/Uses
In everyday beauty formulas, hydroxystearic acid serves more than one purpose, making it a versatile addition.
- Cleansing: Its fatty structure can bind to oil, dirt and makeup so they rinse away with water, helping create a product that leaves skin feeling fresh rather than stripped
- Emulsifying: Acts like a bridge between water and oil, stabilizing creams and lotions so they stay smooth, resist separation and deliver an even layer of moisture or active ingredients
Who Can Use Hydroxystearic Acid
Hydroxystearic acid is generally considered suitable for normal, dry and combination skin because it helps cleanse without stripping and supports a stable cream texture that feels light on the skin. Oily and acne-prone skin types typically tolerate it as well, although very blemish-prone individuals might prefer to monitor how their skin responds since any fatty acid can in rare cases feel too rich for them. Sensitive skin usually gets along with it thanks to its plant origin and low fragrance content but, as always, those with a history of reacting to fatty acids should stay alert to how their skin feels after use.
The ingredient is plant-derived from castor oil so it fits vegan and vegetarian lifestyles. No animal by-products are used at any point in the standard production process.
Current data shows no specific concerns for topical use in pregnancy or while breastfeeding. That said, this is not medical advice and anyone who is pregnant or nursing should run any new skincare product past a qualified healthcare provider just to be safe.
Hydroxystearic acid is not known to cause photosensitivity, so it will not make skin more prone to sunburn. Normal daily sun protection practices still apply if the finished product does not already contain SPF.
Potential Side Effects/Adverse Reactions
Reactions to topical hydroxystearic acid can vary from person to person. The points below outline potential side effects only and most users will not experience them when the ingredient is formulated and used correctly.
- Mild redness or stinging: Usually short-lived and more likely if skin is already compromised or freshly exfoliated
- Allergic contact dermatitis: An uncommon immune response that can lead to itching, swelling or a rash
- Clogged pores or breakouts: Possible in very blemish-prone skin if the overall formula is too rich for that individual
- Eye irritation: Watery eyes or a burning sensation if the product accidentally gets into the eye area
If any of these effects occur stop using the product and consult a healthcare professional or dermatologist for guidance.
Comedogenic Rating
Rating: 1/5
Hydroxystearic acid is a mid-chain fatty acid with a single hydroxyl group that makes it more water-tolerant than many other fatty acids. This slight polarity helps it rinse away more easily, lowering its tendency to settle in pores and create blockages. Most formulators use it at low levels for texture support rather than as a heavy emollient, further reducing the risk of pore clogging.
Overall, it is generally suitable for acne-prone or breakout-prone skin, though tolerance can vary from person to person.
Keep in mind that the final comedogenicity of any product also depends on the full ingredient mix and how often it is used.
Summary
Hydroxystearic acid works in three main ways: it binds to oil and debris for gentler cleansing, bridges water and oil phases to stabilize emulsions and lends a light thickening effect that gives creams a smooth glide without a greasy feel. Thanks to these multitasking abilities it is a quiet workhorse in cleansers, lotions, masks and even sunscreens, though it rarely gets headline hype.
The ingredient is widely regarded as safe for topical use with a low rate of irritation or sensitization. As with any new skincare ingredient it is wise to perform a small patch test when trying a product that contains it, especially if you have very reactive or acne-prone skin.