What Is Hydrogenated Castor Oil/Adipic Acid Copolymer?
Hydrogenated Castor Oil/Adipic Acid Copolymer is a wax-like material made when castor oil that has been fully hydrogenated is linked with adipic acid. Castor oil comes from the seeds of the castor bean plant while adipic acid is a lab-made dibasic acid often used in food and cosmetic production. When the two are combined they create a stable copolymer that is more solid and less greasy than plain castor oil yet still keeps many of its skin friendly qualities.
The cosmetic industry started turning to castor oil derivatives in the mid-20th century because pure castor oil can feel heavy on the skin. Chemists discovered that reacting hydrogenated castor oil with adipic acid made a smoother more workable ingredient that blended easily into creams and lotions without separating. Today the copolymer is produced in large heated reactors where the two raw materials are mixed under controlled temperature and pressure then purified and milled into fine flakes or pellets.
You will spot Hydrogenated Castor Oil/Adipic Acid Copolymer in moisturizers masks sun care products lip balms hair creams solid perfumes makeup sticks and even some baby care formulas. Its ability to thicken a product while adding a soft cushiony feel makes it popular for both water based and anhydrous (water-free) systems.
Hydrogenated Castor Oil/Adipic Acid Copolymer’s Cosmetic Benefits/Uses
This multitasking ingredient supports both the feel and performance of a formula
- Humectant: Helps draw small amounts of water from the air or deeper skin layers toward the surface so skin feels hydrated and looks smoother
- Skin conditioning: Leaves a light protective film that softens rough patches and improves overall texture giving the skin a healthy conditioned appearance
- Emollient: Fills in tiny gaps between skin cells creating a silky finish that reduces flakiness and provides immediate softness without a heavy oily residue
Who Can Use Hydrogenated Castor Oil/Adipic Acid Copolymer
This ingredient is generally well tolerated by all skin types including dry, normal, combination, oily and sensitive skin. Its lightweight waxy texture seals in moisture without leaving a greasy film so even easily congested skin usually handles it well. People with very acne-prone skin who notice that heavy occlusives trigger breakouts may still prefer to patch test products that contain larger amounts of the copolymer.
Hydrogenated Castor Oil/Adipic Acid Copolymer is sourced from castor beans and a lab-made acid, with no animal-derived substances involved, making it suitable for vegans and vegetarians.
The Cosmetic Ingredient Review panel and global regulatory bodies consider this material safe for use during pregnancy and while breastfeeding. That said this is not medical advice and anyone who is pregnant or nursing should have a quick chat with a healthcare professional before starting any new skincare product to be safe.
The copolymer does not increase photosensitivity so it will not make skin more prone to sunburn. It is also odorless and free of known endocrine disruptors, fragrance allergens or essential oil constituents which reduces the chance of irritation for users with reactive skin.
Potential Side Effects/Adverse Reactions
Individual responses to topical ingredients vary. The effects listed below are potential outcomes and are unlikely to occur for most people when the ingredient is used at standard cosmetic concentrations.
- Mild redness or itching – can occur in people who have a castor oil allergy or very reactive skin
- Temporary clogged pores – possible in users who already experience comedonal acne, especially if the surrounding formula is rich in other waxes or butters
- Watery eyes or stinging – may happen if a product containing the copolymer accidentally enters the eye area during application
- Contact dermatitis – rare but may appear as a rash or bumps if the skin develops sensitivity to castor derivatives over time
If any irritation, swelling or persistent discomfort develops stop using the product and seek advice from a healthcare professional.
Comedogenic Rating
Rating: 1/5 (low)
The molecule is a large waxy polymer that sits on the surface rather than sinking deeply into pores, so it is far less likely to plug follicles than heavier butters or poorly refined oils. It keeps some of castor oil’s slip but its hydrogenated structure makes it less sticky, further reducing the risk of buildup. For most people, even those with combination skin, it will not trigger breakouts.
Suitable for acne-prone users in typical leave-on or rinse-off formulas.
As with any low-comedo ingredient, the final product’s overall oil and wax load plus personal skin habits will ultimately decide clogging potential.
Summary
Hydrogenated Castor Oil/Adipic Acid Copolymer works as a humectant, skin conditioner and emollient. It attracts a touch of moisture, smooths rough spots and leaves a soft protective film that feels silky instead of greasy. These traits come from its balanced structure: the castor portion offers glide while the adipic link gives firmness so it can thicken creams, balms and sticks without making them heavy.
It is a solid choice for formulators who need a vegan friendly, odorless texture enhancer which explains why you will find it in a growing number of moisturizers, sunscreens and makeup sticks even if it is not a headline ingredient that shoppers look for by name.
Safety tests and long market use show a very low risk of irritation or allergy, and global regulators allow it in both adult and baby care. Still, whenever you pick up a new product it is smart to patch test first to confirm your skin is happy with the full recipe.