What Is Polyurethane-78?
Polyurethane-78 is a man-made polymer created through a multi-step reaction that starts with soy acid, phthalic anhydride and pentaerythritol. These raw materials produce a urethane precursor that is then linked together with saturated methylene diphenyl diisocyanate, forming a flexible yet durable network often referred to as a polyurethane resin. First explored for industrial coatings in the mid 1900s, lighter cosmetic-grade versions gained popularity in the early 2000s when brands began looking for plant-influenced ingredients that could deliver long-lasting wear without a heavy feel. The result is a clear, almost weightless film former that dissolves easily in standard cosmetic solvents and dries quickly on skin or hair. You will most often see Polyurethane-78 in long-wear mascara, liquid eyeliner, brow gels, transfer-resistant foundations, setting sprays, nail polish top coats and some flexible hold hair stylers.
Polyurethane-78’s Cosmetic Benefits/Uses
In formulas, Polyurethane-78 mainly serves two performance-boosting roles
- Binding: Acts like a glue that keeps pigment, shimmer and other particles evenly dispersed so the product applies smoothly and stays uniform from first swipe to last wear. Better binding means less settling in the bottle and fewer touch-ups on the face.
- Film Forming: Creates an invisible, breathable layer on skin, lashes or hair that locks color in place and resists smudging, water and sweat. This lightweight film also adds a soft, flexible finish that prevents cracking or flaking, improving comfort and overall wear time.
Who Can Use Polyurethane-78
Thanks to its lightweight breathable film Polyurethane-78 is generally considered suitable for all skin types including oily dry combination and even mature skin. Because it does not form an overly occlusive barrier most people find it comfortable and non-greasy. Those with very reactive or eczema-prone skin should still watch for any stinging or redness since any synthetic polymer can occasionally trigger sensitivity.
The ingredient is made from plant-derived soy acid and fully synthetic chemicals with no animal-sourced components so it is compatible with vegan and vegetarian lifestyles provided the finished product is free of other animal ingredients.
No reproductive toxicity studies have raised red flags for topical use and the large molecular size means it is unlikely to cross the skin barrier. That said pregnant or breastfeeding individuals should ask their health professional before adding any new cosmetic product to their routine as a general safety measure and nothing here should be taken as medical advice.
Polyurethane-78 does not absorb UV light so it does not make skin more sensitive to the sun. It can however form a durable film that may require a thorough oil-based cleanser for complete removal especially around the eyes.
Potential Side Effects/Adverse Reactions
Responses to topical Polyurethane-78 vary from person to person. The following are potential side effects that have been reported in rare cases and are not expected for the average user when products are formulated correctly.
- Mild skin irritation such as redness itching or a burning sensation
- Allergic contact dermatitis in individuals sensitized to isocyanate-based polymers
- Eye watering or stinging if the product migrates into the eye area before it sets
- Temporary buildup or stiffness on hair shafts leading to dullness if not cleansed thoroughly
- Very rare clogging of pores in acne-prone users when combined with heavy occlusive ingredients
If any discomfort swelling or persistent irritation occurs stop using the product immediately and seek advice from a qualified healthcare provider.
Comedogenic Rating
Rating: 1/5. Polyurethane-78 is a high-molecular-weight film former that sits on the surface rather than soaking into pores, and it is not oily by nature. This keeps its clogging potential low, though very sensitive or acne-prone users might notice issues if the polymer is blended with heavy waxes or butters in a finished formula. Overall it is considered safe for breakout-prone skin.
Formulation matters: in a lightweight water-based mascara or setting spray, Polyurethane-78 poses almost no risk of congestion, while in a thick cream it may raise the chance slightly due to the other ingredients present.
Summary
Polyurethane-78 mainly works as a binder and film former, holding pigments in place and creating a thin breathable layer that resists water, sweat and smudging. This makes makeup apply smoothly, last longer and stay comfortable.
Its popularity has grown steadily in long-wear cosmetics such as mascaras, eyeliners, foundations and nail top coats, though it is still a niche choice compared with silicones and traditional acrylates.
Current safety data shows a very low risk of irritation or systemic absorption thanks to its large molecular size and inert structure. As with any new cosmetic ingredient it is smart to perform a quick patch test when trying products that contain Polyurethane-78, especially if you have sensitive or reactive skin.