What Is Polysilicone-31?
Polysilicone-31 is a specialty silicone made from repeating siloxane units that are capped with a 3-hydroxypropyl group, then linked to long C18 fatty acid dimers finished with branched ester chains. In plain terms it is a hybrid of silicone and lightweight plant-derived lipids. This unique make-up allows it to create a flexible layer on the skin without feeling greasy.
Silanes and silicones entered beauty labs in the 1950s as chemists looked for ingredients that could resist water yet feel silky. Over time suppliers tweaked the backbone of these molecules to fine-tune feel and performance. Polysilicone-31 is one of these later developments, designed to form a smooth film while still letting skin breathe. It rose to popularity in the early 2000s when formulators wanted longer-lasting wear in color cosmetics and sun care without the heavy feel of older resins.
Manufacturing starts with dimethylsiloxane chains that are reacted with 3-chloropropyl groups. This step adds the sites needed to attach the fatty acid dimers. The fatty dimers, often sourced from vegetable oils, are then esterified with branched octyl and dodecyl alcohols before being grafted onto the silicone backbone. The result is a high-molecular-weight liquid or soft solid that disperses easily in oils or silicones.
You will find Polysilicone-31 in long-wear foundations, BB creams, primers, waterproof mascaras and eyeliners, transfer-resistant lip colors, sunscreens, setting sprays and some hair styling products that aim for humidity resistance.
Polysilicone-31’s Cosmetic Benefits/Uses
In formulas Polysilicone-31 acts mainly in one key way, yet that single role covers several performance gains for both the product and the user.
Film forming: It lays down a thin flexible layer that anchors pigments, UV filters and other actives to the skin or hair. This improves wear time, water resistance and smudge resistance, helps color stay true through the day and keeps sunscreens from rinsing off too quickly. The film also gives a soft-focus finish that can blur fine lines and uneven texture while still allowing the skin to breathe and move naturally.
Who Can Use Polysilicone-31
Polysilicone-31 is generally well tolerated by all skin types including dry, oily and combination. Its lightweight flexible film does not trap heat or sweat so even sensitive or acne-prone skin usually handles it without issue. Those with very reactive skin should still pay attention to how their skin feels because any film former can occasionally feel occlusive on extremely delicate complexions.
The ingredient is synthetic and made without animal-derived substances so it is suitable for vegans and vegetarians.
No specific warnings exist for pregnant or breastfeeding women. Current safety data show low skin penetration and minimal systemic exposure. That said this is not medical advice and anyone who is pregnant or nursing should discuss all skincare products with a healthcare professional to be safe.
Polysilicone-31 does not make skin more sensitive to sunlight and has no known interactions with UV exposure. It can actually boost the water resistance of sunscreens by keeping UV filters in place.
Potential Side Effects/Adverse Reactions
Reactions to topical Polysilicone-31 differ from person to person. The points below list possible but uncommon issues. When the ingredient is used correctly in a well-formulated product most people will not notice any negative effects.
- Mild skin irritation Redness or itching can occur on very sensitive skin if the film traps heat or sweat
- Transient clogged pores Heavy layers or pairing with rich oils may feel occlusive on skin already prone to congestion
- Eye discomfort If a product containing Polysilicone-31 runs into the eyes it can cause temporary stinging or watering
- Contact dermatitis A rare allergy to the silicone or attached fatty esters could lead to localized rash
If any of these effects appear stop using the product and consult a healthcare provider for guidance.
Comedogenic Rating
Rating: 1/5
Polysilicone-31 molecules are large and remain on the surface so they do not sink into pores. The breathable film they create allows air and water vapor to pass through which keeps sebum from building up. While the attached fatty acid esters sound heavy they are branched and lightweight so they behave more like dry oils than thick occlusives. All of this places the ingredient very low on the clogging scale though any film former can hold in oil if applied in thick layers.
Overall the ingredient is considered suitable for acne-prone or breakout-prone skin.
If a formula also contains rich butters waxes or heavy oils that combination could raise the product’s overall comedogenicity even if Polysilicone-31 itself is low risk.
Summary
Polysilicone-31 is a silicone-lipid polymer that lays down a thin flexible film keeping pigments UV filters and styling agents in place. This boosts wear time adds water and smudge resistance and delivers a soft focus feel without greasiness.
It is not as widely known as classics like dimethicone yet it is gaining ground in long-wear makeup sunscreens and humidity-proof hair products because it offers durability plus a light touch.
Safety data shows very low irritation or penetration so most users tolerate it well. Even so it is wise to patch test any new product to be sure it agrees with your skin.