What Is Polyester-37?
Polyester-37 is a man-made polymer created by reacting hexanedioic acid with 2,2′-(methylimino)bis[ethanol] and 1,2,3-propanetriol, then capping the chain with isooctadecanoic acid. The result is a smooth, flexible film-forming material that disperses well in oils and some water-based systems. First introduced in the 1990s as cosmetics shifted toward longer-lasting finishes, it quickly found favor for its lightweight feel and strong yet breathable film.
Manufacturing follows a controlled condensation process where the base acids and alcohols are heated under vacuum. Water that forms during the reaction is removed, driving the chain growth. Once the target molecular weight is reached, the mixture is esterified with isooctadecanoic acid to improve softness and spreadability. The final solid or semi-solid resin is cooled, milled and shipped to formulators.
You will most often spot Polyester-37 in products that need flexible hold or extended wear. Hair sprays, styling creams and pomades rely on it for touchable control. Makeup items such as foundations, primers, liquid lipsticks and mascaras use it to resist smudging. Skincare formulas including moisturizers, sunscreens and sheet masks take advantage of its smooth feel and moisture-sealing film.
Polyester-37’s Cosmetic Benefits/Uses
In everyday beauty products Polyester-37 serves several helpful roles:
- Film forming: Creates an even, breathable layer on skin or hair that locks pigments in place, boosts water resistance and gives makeup longer wear without heaviness.
- Hair conditioning: Coats each strand with a thin flexible film that smooths cuticles, reduces frizz and adds soft shine while still allowing natural movement.
- Skin conditioning: Leaves a silky finish that helps trap moisture, lessens tackiness in creams and improves the spread of actives for a more comfortable feel.
Who Can Use Polyester-37
Polyester-37 is considered friendly for most skin and hair types thanks to its lightweight film that sits on the surface rather than soaking deeply into pores. Dry or normal skin often enjoys the extra moisture-trapping layer while oily or combination skin appreciates that the ingredient feels non-greasy and does not add extra shine. Very acne-prone users may want to keep an eye on how their skin responds in case the film locks in excess oil or mixes with heavy waxes in a formula, though Polyester-37 alone is not known for causing breakouts.
The polymer is fully synthetic and contains no animal-derived material, so it is suitable for vegans and vegetarians. Manufacturing does not rely on animal testing in most regions, yet consumers who follow cruelty-free guidelines should still confirm the finished brand’s stance, since regulations differ by country.
No specific warnings exist for pregnant or breastfeeding individuals. The molecule is large, stays on the surface and is not expected to reach the bloodstream. This is not medical advice and anyone who is expecting or nursing should check with a doctor before starting new personal care products just to be safe.
Polyester-37 does not make skin more sensitive to the sun and has no known interaction with UV light. It can even boost the water resistance of sunscreens by helping the active filters stay in place. People with very sensitive eyes might notice a filmy feeling if the ingredient is used in mascara or eyeliner, but this is uncommon.
Potential Side Effects/Adverse Reactions
Side effects from topical Polyester-37 vary from person to person. The points below outline potential reactions, yet most users will not experience them when the ingredient is formulated and used correctly.
- Mild skin irritation or redness
- Temporary clogged pores in very acne-prone skin when combined with heavy oils or waxes
- Build-up on hair leading to limp strands if products are not cleansed away regularly
- Eye discomfort or watering if the film flakes into the eye area
- Contact allergy marked by itching or small rash in those with sensitivity to synthetic esters
If any of these effects occur discontinue use and consult a healthcare professional or dermatologist for guidance.
Comedogenic Rating
Rating: 1/5
Polyester-37 earns a low score because its large, inert polymer chains sit on the surface without melting into pores or acting like heavy oils. While the thin film can slow down natural oil evaporation, it is not greasy itself and is easily removed with regular cleansing, so blockage risk is minimal.
This makes Polyester-37 generally acceptable for acne-prone skin, provided the overall formula is light and properly removed at the end of the day.
Keep in mind the finished product’s other ingredients can raise or lower the real-world clogging potential, so always look at the full label when judging suitability.
Summary
Polyester-37 works as a film former, hair conditioner and skin conditioner by creating a smooth, flexible microfilm that locks pigments in place, tames frizz and seals in moisture while leaving a lightweight feel. Its popularity sits in the middle of the pack: not a buzzword ingredient like hyaluronic acid yet quietly present in many long-wear cosmetics, sunscreens and styling products because it delivers dependable performance.
Safety studies and years of use show a low risk of irritation or sensitization, with only rare reports of mild contact allergy. Still, skin can be unpredictable so it is wise to patch test any new product containing Polyester-37 before full use.