What Is Isobutylene/Ethylmaleimide/Hydroxyethylmaleimide Copolymer?
Isobutylene/Ethylmaleimide/Hydroxyethylmaleimide Copolymer is a synthetic polymer made by linking together three building blocks: isobutylene, ethylmaleimide and hydroxyethylmaleimide. The first unit, isobutylene, comes from petroleum refining and is valued for producing flexible yet durable chains. The maleimide units add small nitrogen-containing rings that help the finished polymer form a smooth uniform film on skin or hair. When chemists combine these monomers under heat and pressure in the presence of a catalyst, they create long molecules that behave a bit like a clear elastic net.
Polymers that sit on the surface have been used in cosmetics since the 1950s when hairstyling sprays first appeared. This particular copolymer was introduced later to give formulators a way to get strong hold without a stiff or flaky feel. Because it dissolves in alcohol or certain water-compatible solvents, it can be blended into modern low-VOC sprays, creams and gels.
You will most often find Isobutylene/Ethylmaleimide/Hydroxyethylmaleimide Copolymer in hair sprays, styling gels, mousses, edge-taming creams and lash or brow products. Some long-wear makeup items such as liquid eyeliners or eyebrow pens also use it to anchor pigments so they resist smudging.
Isobutylene/Ethylmaleimide/Hydroxyethylmaleimide Copolymer’s Cosmetic Benefits/Uses
This ingredient plays two main roles in beauty formulas
- Film forming: It dries to a thin flexible layer that locks in active ingredients, helps makeup last longer and shields hair or skin from humidity and pollution
- Hair fixing: The polymer creates strong yet touchable hold so styles stay put through movement and moisture while still allowing hair to bend and look natural
Who Can Use Isobutylene/Ethylmaleimide/Hydroxyethylmaleimide Copolymer
This polymer sits on the surface rather than soaking in so it is generally well tolerated by all skin types including dry, normal, oily and sensitive. Because it forms a breathable film without heavy oils it will not usually weigh down oily skin or hair, though people who struggle with very clogged pores might prefer lighter application to avoid build-up.
The ingredient is synthesized from petrochemical feedstocks and contains no animal derived substances so it is suitable for vegans and vegetarians as long as the rest of the formula is also animal free.
No data suggests that topical use poses a risk during pregnancy or while breastfeeding and the large polymer molecules are unlikely to penetrate deeply enough to reach the bloodstream. That said this is not medical advice and anyone who is pregnant or nursing should review all personal care products with a healthcare provider.
Isobutylene/Ethylmaleimide/Hydroxyethylmaleimide Copolymer does not trigger photosensitivity so it can be worn during daytime without extra sun precautions beyond a normal sunscreen routine.
Potential Side Effects/Adverse Reactions
- Rare allergic contact dermatitis marked by redness itching or rash
- Mild eye or respiratory irritation if the spray form is inhaled before it dries
- Temporary hair stiffness flaking or dullness when excessive layers are applied
- Build up on scalp or skin that may clog follicles in very oily or acne prone users
- Greater flammability risk when paired with high alcohol hair sprays used near open flame
If any adverse reaction occurs stop using the product and seek advice from a medical professional.
Comedogenic Rating
Rating: 1/5. Isobutylene/Ethylmaleimide/Hydroxyethylmaleimide Copolymer is a large, non-oily molecule that stays on the surface and is removed with normal cleansing so it has very little tendency to block pores. Only in rare cases where heavy layers are left on for several days could it mingle with sebum and trap debris. Overall it is considered suitable for acne-prone or breakout-prone skin.
Because the ingredient is often delivered in alcohol-based sprays rather than creamy bases, most formulas using it are also light in emollients, further lowering clogging risk.
Summary
Isobutylene/Ethylmaleimide/Hydroxyethylmaleimide Copolymer is a film former and hair-fixing agent that dries to a clear flexible mesh. This mesh locks makeup or styling products in place, shields against humidity, holds hairstyles steady, and helps pigments stay put without flaking. It works by creating long intertwined polymer chains that sit uniformly on skin or hair then harden as the solvent evaporates.
While not as famous as classic styling resins like PVP or acrylates, it has a steady presence in modern long-wear and edge-control products because it offers strong hold with a softer feel. Formulators appreciate its ability to meet low-VOC regulations and its compatibility with both alcohol and water-compatible solvents.
Safety data show a low irritation profile, minimal pore-clogging potential, and no known systemic concerns, so most users can apply products containing this polymer without worry. As with any new cosmetic, doing a quick patch test on a small area is still the smartest way to confirm personal tolerance.