What Is C18-38 Alkyl Hydroxystearoyl Stearate?
C18-38 Alkyl Hydroxystearoyl Stearate is an ester created by linking hydroxystearic acid, stearic acid and a blend of long-chain (18 to 38 carbon) fatty alcohols. The result is a wax-like material that is solid at room temperature yet melts smoothly on skin contact. Most manufacturers derive the fatty acids and alcohols from plant oils such as coconut, palm or rapeseed then refine and react them through esterification, a process that joins the acid and alcohol portions while removing water. The ingredient first appeared in the early 2000s when formulators searched for plant-based alternatives to mineral waxes, and it quickly gained favor for its versatility in modern “green” formulations.
Today you will find C18-38 Alkyl Hydroxystearoyl Stearate in moisturizers, facial masks, lip balms, stick foundations, anti-aging creams, sunscreens, hair conditioners and makeup primers. Its balance of cushion and slip makes it a popular choice for both skincare and color cosmetics where stability and a soft, velvety skin feel are essential.
C18-38 Alkyl Hydroxystearoyl Stearate’s Cosmetic Benefits/Uses
Formulators value this multifunctional ingredient for the way it improves texture, stability and overall skin feel in a wide range of products.
- Emulsion stabilising: Helps oil and water phases stay uniformly blended so creams and lotions remain smooth during storage and application
- Emollient: Forms a light protective film that softens skin, reduces moisture loss and leaves a silky after-feel without heaviness
- Viscosity controlling: Thickens formulations just enough to create a rich, non-greasy texture that spreads easily and stays put on the skin
Who Can Use C18-38 Alkyl Hydroxystearoyl Stearate
This ingredient suits most skin types, particularly normal, dry or combination skin that benefits from extra softness and a controlled, cushiony texture. Oily or acne-prone skin can usually tolerate it as well, though the waxy nature of the ester might feel heavy on very oily complexions so those users may prefer lighter formulas.
C18-38 Alkyl Hydroxystearoyl Stearate is made from plant-derived fatty acids and alcohols so it is typically considered vegan and vegetarian friendly provided the finished product has not been tested on animals and no animal-based additives have been mixed in.
The large molecular size keeps it on the surface of the skin which is why formulators view it as low risk for systemic absorption. For that reason it is generally regarded as safe for people who are pregnant or breastfeeding. This is not medical advice and anyone who is expecting or nursing should still ask their doctor before adding new skincare products, just to be safe.
The ester does not make skin more sensitive to sunlight so there is no added risk of photosensitivity. It can also be used alongside most common actives such as retinoids, vitamin C and exfoliating acids without stability issues.
Potential Side Effects/Adverse Reactions
Side effects from topical use of C18-38 Alkyl Hydroxystearoyl Stearate can vary from one person to another. The points below list potential reactions yet most users will not encounter them when the ingredient is properly formulated and used as directed.
- Mild skin irritation such as redness or itching in very sensitive individuals
- Temporary clogged pores or breakouts on highly oily or acne-prone skin
- Contact allergy presenting as rash or swelling, though reports are rare
- Greasy or heavy feel if layered with multiple rich products
If you notice any unwanted reaction stop using the product and seek medical advice if symptoms persist or worsen.
Comedogenic Rating
Rating: 2 out of 5 (low to moderate)
C18-38 Alkyl Hydroxystearoyl Stearate is derived from long-chain fatty acids, which can sometimes sit on the surface and mingle with sebum, yet its large ester structure keeps it from penetrating deeply into pores. Most users will not notice clogged pores unless they are extremely oil-prone or layer several rich products at once. Overall it is considered suitable for acne-prone skin when used in light or well-balanced formulas, though very breakout-prone individuals may prefer to monitor how their skin responds.
Because this ingredient is typically used at low to moderate percentages and is balanced by other emulsifiers, its likelihood of causing widespread congestion is lower than that of pure fatty acids or heavy butters.
Summary
C18-38 Alkyl Hydroxystearoyl Stearate acts as an emulsion stabiliser, an emollient and a viscosity controller. Its waxy yet melt-on-contact texture keeps oil and water phases blended, cushions the skin with a soft protective film and thickens formulas just enough for a rich silky feel without greasiness.
While not as famous as shea butter or jojoba oil, this plant-derived ester has gained steady popularity in modern moisturisers, makeup sticks and clean beauty formulas thanks to its versatility and pleasant skin finish.
Safety data and decades of use point to a low risk of irritation or systemic absorption, making it generally safe for most skin types including sensitive, pregnant or breastfeeding users. As with any new cosmetic ingredient it is wise to patch test a new product first to be sure your skin agrees.