What Is 3-Hydroxybutyrate/4-Hydroxybutyrate Copolymer?
3-Hydroxybutyrate/4-Hydroxybutyrate Copolymer is a man-made polymer created from two naturally occurring building blocks, 3-hydroxybutyric acid and 4-hydroxybutyric acid. When these small acids are linked together they form a larger, biodegradable chain that looks and feels like a gentle plastic powder. Originally explored in the late 1990s as an eco-friendly alternative to petroleum-based plastics, scientists soon noticed that the fine particles were smooth enough for skin care use and began testing them in topical formulas.
The copolymer is made through a controlled fermentation process. Friendly bacteria are fed plant-derived sugars, which they convert into the two hydroxybutyrate acids. These acids are then purified and chemically linked through a safe, solvent-free reaction. The final powder is sifted to achieve a uniform particle size suited for cosmetics.
Because it is mild, biodegradable and versatile, you can now find 3-Hydroxybutyrate/4-Hydroxybutyrate Copolymer in a range of rinse-off and leave-on products. Facial scrubs, cream cleansers, clay masks, exfoliating body washes, lightweight lotions and even some anti-aging serums use it to improve texture or stability.
3-Hydroxybutyrate/4-Hydroxybutyrate Copolymer’s Cosmetic Benefits/Uses
This ingredient plays two main roles in skin care formulas
- Abrasive – The smooth round particles provide gentle physical exfoliation. They help lift away dead skin cells and surface debris without scratching, leaving skin feeling softer and looking brighter.
- Viscosity controlling – The powder can thicken a formula or keep tiny ingredients evenly suspended. This helps creams, gels and washes maintain a pleasant, uniform feel from the first use to the last.
Who Can Use 3-Hydroxybutyrate/4-Hydroxybutyrate Copolymer
This ingredient is generally well tolerated by all major skin types. Normal, oily, combination and dry complexions can use it without trouble. Sensitive or barrier-impaired skin should start slowly because any physical exfoliant can feel rough if the skin is already inflamed. People dealing with active rosacea flares or open eczema patches may prefer to skip grain-based scrubs until the skin calms down.
The copolymer is made through a plant-based fermentation process and contains no animal derivatives, so it fits vegan and vegetarian lifestyles. As always, final product certifications depend on the brand’s overall manufacturing choices.
No research shows that the polymer poses a risk to women who are pregnant or breastfeeding when used topically. The particles do not penetrate deeply and are often rinsed away. Still, this is not medical advice and anyone who is expecting or nursing should run new products past a healthcare professional.
The ingredient does not cause photosensitivity, so it will not make skin more prone to sunburn. Standard daily sunscreen is still recommended to protect freshly exfoliated skin.
Potential Side Effects/Adverse Reactions
Individual responses can differ. The points below cover possible reactions, but most users will not encounter them when the ingredient is formulated and used correctly.
- Mechanical irritation such as tingling or mild scratching if applied with heavy pressure
- Temporary redness in very sensitive skin
- Dryness or tightness if over-exfoliation removes too much surface oil
- Rare allergic contact dermatitis leading to itching or small bumps
- Eye irritation if particles accidentally enter the eyes during rinsing
If any of these effects occur, discontinue use and seek advice from a qualified healthcare provider if symptoms persist.
Comedogenic Rating
Rating: 0–1 out of 5. 3-Hydroxybutyrate/4-Hydroxybutyrate Copolymer is an inert, water-insoluble particle that sits on the surface and is rinsed away, so it has little chance of blocking pores. It contains no oils, waxes or fatty acids that typically trigger congestion. Because of this low clogging potential it is generally suitable for people prone to acne or breakouts. Formulas that combine the polymer with heavy plant butters or silicones could change overall pore-clogging risk, so check the full ingredient list.
Summary
3-Hydroxybutyrate/4-Hydroxybutyrate Copolymer gently buffs away dead cells as a mild abrasive and stabilises textures by keeping ingredients evenly dispersed. These two roles help products feel smoother, last longer and leave skin looking fresher.
While eco-minded brands have embraced this biodegradable polymer, it remains a niche alternative to more common exfoliating beads or thickeners. Limited supply and higher production costs keep it from mainstream shelves for now.
Current research and real-world use show the ingredient is safe for most skin types with a very low irritation and comedogenic profile. As with any new skincare product a quick patch test on a small area is a smart way to rule out personal sensitivities before full-face use.