What Is Polyester-34?
Polyester-34 is a man-made polymer created when dilinoleic acid joins with polyglycerin-3 and bis-hydroxypropyl dimethicone, then capped with a blend of stearic acid and isostearic acid. This mix of fatty acids and silicone segments gives the material a flexible feel that spreads easily on skin.
The idea of combining plant-based fatty acids with silicone chemistry gained traction in the late 1990s as formulators searched for milder alternatives to heavy mineral oils. Polyester-34 emerged from this research and has been used in commercial cosmetics for more than a decade, prized for adding a silky finish without greasiness.
Production starts with dilinoleic acid sourced from plant oils such as soybean or sunflower. Chemists react it with polyglycerin-3, a short chain of glycerin units, to build the polyester backbone. Bis-hydroxypropyl dimethicone is then added to introduce silicone segments that enhance slip and water resistance. Finally stearic and isostearic acids close off the chain to control the polymer’s length and texture. The result is a waxy solid that is melted and blended into creams and lotions.
You will most often see Polyester-34 in facial moisturizers, body creams, makeup primers, sheet masks, hair conditioners and anti-aging serums where a smooth cushiony feel is desired.
Polyester-34’s Cosmetic Benefits/Uses
In formulas Polyester-34 delivers two key functions that improve both texture and skin feel:
- Skin conditioning – Helps soften and smooth the skin surface so it feels hydrated and comfortable after application
- Emollient – Forms a light protective film that fills in tiny skin gaps, reducing roughness and giving products a creamy glide without feeling heavy
Who Can Use Polyester-34
Polyester-34 is gentle enough for most skin types, including normal, dry and combination skin that benefits from extra softness. Its lightweight film does not feel greasy so it can also suit oily skin, though very acne-prone users may prefer to patch-test products that pair it with richer oils. Those with sensitive skin usually tolerate the ingredient well because it is chemically stable and free of common irritants.
The polymer is made from plant-sourced fatty acids and laboratory-made silicone segments, with no animal-derived components, so it is generally considered suitable for vegans and vegetarians. If you follow a strict lifestyle, confirm that the brand uses vegetable-origin stearic acid in its supply chain.
Current safety data show no specific risks for people who are pregnant or breastfeeding when Polyester-34 is applied topically. Because every pregnancy is unique this is not medical advice; expecting or nursing mothers should review any skincare routine with their doctor to stay on the safe side.
Polyester-34 does not increase photosensitivity, meaning it will not make skin more prone to sunburn. It is odorless, has no known hormonal activity and does not interfere with common actives like vitamin C or retinol, so it can be layered comfortably in most routines.
Potential Side Effects/Adverse Reactions
Reactions to topical Polyester-34 vary from person to person. The points below list potential side effects that are unlikely for the average user when the ingredient is formulated and used correctly.
- Mild skin irritation – rare redness or itching if the individual is sensitive to fatty acids or silicones
- Transient clogged pores – possible in very acne-prone skin when the ingredient is combined with heavier oils
- Contact dermatitis – uncommon allergic response resulting in rash or swelling
- Build-up on hair shafts – in leave-in conditioners it may require clarifying shampoo if used frequently
If you notice any persistent discomfort or visible reaction stop using the product and consult a healthcare professional
Comedogenic Rating
Rating: 1/5
Polyester-34 forms a very thin silicone-fatty acid film that lets skin breathe instead of plugging pores. The linoleic backbone is naturally low in clogging potential and the added dimethicone segments are classified as non-comedogenic. A touch of stearic and isostearic acid introduces a slight risk, so the score is not a perfect zero.
In most formulas this ingredient is considered safe for acne-prone skin, though overall pore-friendliness still depends on the rest of the product.
Heavier textures or very occlusive companions like petrolatum can raise the clogging potential even when Polyester-34 itself is low, so read full ingredient lists if breakouts are a concern.
Summary
Polyester-34 mainly works as a skin conditioner and emollient, melting into a soft film that smooths rough patches, fills micro-gaps and leaves a silky afterfeel without greasy weight. The silicone segments boost slip while the plant-based fatty acids add cushion so products spread evenly and feel hydrating.
Although not a headline ingredient like hyaluronic acid, it shows up quietly in moisturizers, primers and masks because formulators value its balanced texture and stability. Usage has grown steadily over the past decade as brands look for lightweight alternatives to heavier oils.
Current evidence points to a low rate of irritation or pore blockage when used as directed, making Polyester-34 a generally safe choice for most skin types. As with any new cosmetic it is wise to patch test a fresh product first to be certain it suits your individual skin.