What Is Acrylates/Stearyl Methacrylate Copolymer?
Acrylates/Stearyl Methacrylate Copolymer is a synthetic ingredient created by linking stearyl methacrylate with small acrylic or methacrylic acid molecules. The result is a lightweight plastic-like network that disperses easily in water or oil. Chemists began exploring these types of acrylic copolymers in the 1970s when the cosmetics industry needed more reliable thickeners and stabilisers. Today manufacturers produce the copolymer through a process called free-radical polymerisation: the raw monomers are mixed, activated by heat or light, then allowed to bond into long chains before being purified and dried into a fine powder.
Because it keeps formulas smooth and at the right thickness, this copolymer appears in many everyday products. You will spot it in face creams, body lotions, sunscreens, liquid foundations, primers, sheet mask serums, hair styling creams and even some deodorant sticks.
Acrylates/Stearyl Methacrylate Copolymer’s Cosmetic Benefits/Uses
In a formula this ingredient pulls double duty, making products feel pleasant and stay mixed from the first pump to the last.
- Emulsion stabilising – helps oil and water stay blended so creams do not split, giving a uniform texture and longer shelf life
- Viscosity controlling – thickens watery mixtures just enough for a silky spread without heaviness, allowing lotions to glide on evenly and reducing dripping in sprays or serums
Who Can Use Acrylates/Stearyl Methacrylate Copolymer
This copolymer is considered friendly to all main skin types. Dry and mature skin benefit from the smooth, cushiony feel it adds to creams while oily and combination skin appreciate that it thickens formulas without a greasy residue. Those with sensitive skin can usually tolerate it because it is non reactive and does not penetrate deeply, though individuals prone to acrylic allergies should remain cautious.
The ingredient is manufactured from petroleum derived monomers with no animal sourced inputs, making it suitable for both vegans and vegetarians. It is also routinely used in products that comply with cruelty free standards.
Current safety assessments show no reproductive or developmental concerns at the tiny levels used in cosmetics, so products containing Acrylates/Stearyl Methacrylate Copolymer are generally regarded as safe for people who are pregnant or breastfeeding. This is not medical advice and anyone expecting or nursing should discuss new skincare with a doctor to be sure it meets their personal needs.
The polymer does not increase photosensitivity, so it will not make skin more prone to sunburn. It also has no known interactions with common actives like retinoids, vitamin C or exfoliating acids, allowing it to fit easily into most routines.
Potential Side Effects/Adverse Reactions
Responses to topical Acrylates/Stearyl Methacrylate Copolymer can vary from person to person. The issues listed below are possible but unlikely for the average user when the ingredient is used correctly in a well formulated product.
- Mild skin irritation – itching or slight redness, typically in very sensitive individuals or when applied to broken skin
- Contact dermatitis – rare allergic reaction linked to leftover monomer traces in the raw material
- Eye irritation – stinging or watering if the product accidentally gets into the eyes, most relevant for sprays or loose powders
- Product buildup – a filmy feel on hair or skin if layered excessively, more common in leave on products
If any irritation or unusual reaction develops discontinue use and seek advice from a healthcare professional.
Comedogenic Rating
Rating: 0–1. Acrylates/Stearyl Methacrylate Copolymer is a large, water-dispersible molecule that stays on the surface of skin rather than slipping into pores. Because it forms a breathable film and contains no oily fractions it is extremely unlikely to block follicles. For most people, even those with oily or combination skin, this low score means a very small risk of breakouts.
Suitable for acne-prone users.
As with any film-forming ingredient, heavy layering over rich creams can trap other comedogenic substances underneath, so keep the rest of your routine light if congestion is a concern.
Summary
Acrylates/Stearyl Methacrylate Copolymer acts as both an emulsion stabiliser and a viscosity controller. Its acrylic backbone locks oil and water together so lotions stay uniform, while its long stearyl side chains give products a soft body that spreads in a smooth even layer.
The ingredient is a quiet workhorse found in everything from sunscreens to primers. It is not as famous as hyaluronic acid or niacinamide, yet formulators reach for it often because it keeps textures pleasant and reliable.
Current safety reviews show it is non irritating for most skin types, non sensitising and non comedogenic at typical use levels. Still, skin can be unpredictable, so do a quick patch test when trying any new product that contains this copolymer.