Polyurethane-56: What Is It, Cosmetic Uses, Benefits & Side Effects

Curious about this ingredient? In this article we're explaining exactly what it is and why it's used within cosmetic formulations.
Updated on: July 1, 2025
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We verify all information on this page using publicly available nomenclature standards from The Personal Care Products Council (PCPC), the European Commission's CosIng database and documentation provided directly by ingredient manufacturers. Our analysis is based on technical data from these sources to ensure accuracy and reliability.

What Is Polyurethane-56?

Polyurethane-56 is a synthetic polymer made by linking together two main building blocks: a flexible polyether segment and a rigid diisocyanate segment. Chemists combine cyclohexanol derivatives, poly(oxy-1,4-butanediol), and a trimethylcyclohexane diisocyanate, then cap the chain with 2-hydroxypropyl methacrylate. The result is a stable film-forming resin that behaves much like the tougher plastics used in coatings but is optimized for skin and hair contact.

Polyurethane science dates back to the 1930s, yet its move into beauty happened decades later when makeup and hair-care formulators started looking for lightweight hold and long-lasting wear. During the 1990s improved purification methods made cosmetic-grade Polyurethane-56 available, opening the door for its use in color cosmetics, sunscreens, and flexible face masks.

The ingredient is produced in closed reactors where temperature and pH are carefully controlled. Once the monomers join, the resulting polymer is purified, neutralized, and turned into an easy-to-use liquid or fine powder for blending into creams, sprays, or gels.

Today you will most often find Polyurethane-56 in long-wear foundations, waterproof mascaras, liquid lipsticks, peel-off face masks, hair styling creams, and flexible nail polish formulations.

Polyurethane-56’s Cosmetic Benefits/Uses

Polyurethane-56 serves as a binder in formulas, helping all the other ingredients stick together so the product spreads evenly and stays put once applied. Because of its binding action it also acts as a light film former, giving makeup better resistance to sweat or rubbing while keeping the finish smooth and comfortable.

Who Can Use Polyurethane-56

Polyurethane-56 is considered gentle enough for most skin types, including dry skin, oily skin and combination skin, because it sits on the surface as a breathable film rather than sinking deeply into pores. Very sensitive or eczema-prone skin may want to proceed cautiously, as any film former can occasionally trap heat or sweat and trigger discomfort for those already dealing with barrier issues.

The polymer is fully synthetic and contains no animal-derived materials so it is suitable for both vegans and vegetarians. Manufacturers usually produce it under cruelty-free guidelines as well, though shoppers should still verify a brand’s overall animal testing policy.

Available safety data show no specific risks for women who are pregnant or breastfeeding when Polyurethane-56 is used in normal cosmetic amounts. That said, this is not medical advice and anyone who is expecting or nursing should have their healthcare provider review any new skincare or makeup product just to be safe.

The ingredient does not absorb UV light or make skin more sensitive to the sun so it does not create photosensitivity concerns. It is also fragrance-free and non-volatile, meaning it will not irritate airways under normal use.

Potential Side Effects/Adverse Reactions

Side effects and reactions to topical Polyurethane-56 vary from person to person. The points below outline potential issues even though most users will not experience them when the ingredient is properly formulated.

  • Mild skin redness or stinging on very sensitive skin, especially if applied to broken or compromised areas
  • Contact dermatitis triggered by trace residual monomers or solvents left over from production
  • Temporary clogged pores if the film is layered too thickly or not removed thoroughly
  • Eye irritation if mascara or eyeliner containing Polyurethane-56 flakes into the eye
  • Respiratory irritation when inhaled from aerosol hair sprays containing high concentrations

If any of these reactions occur stop using the product and seek medical advice promptly.

Comedogenic Rating

Rating: 1 / 5 (low)

Polyurethane-56 forms a thin breathable film that sits on top of the skin rather than sinking deep into pores. It is not oily and has a large molecular size, so it is unlikely to block follicles on its own. A rating of 1 reflects this low risk while still noting that any film former can trap existing oil or debris if applied in heavy layers or left on overnight without proper cleansing.

Most people prone to acne or breakouts can use products containing Polyurethane-56 without added worry, provided the rest of the formula is also low in pore-clogging ingredients.

As with any resin, the final comedogenic potential depends on how it is blended. Thick waterproof makeup left on for long periods can feel occlusive, so a good removal routine is key.

Summary

Polyurethane-56 is mainly a binder and light film former. It holds pigments and other ingredients together so makeup spreads evenly and stays put, then dries into a flexible layer that resists sweat and rubbing without feeling stiff.

While not as famous as silicones or acrylates, it has carved out a steady place in long-wear foundations, waterproof mascaras, peel-off masks and flexible nail colors thanks to its balance of hold and comfort.

Current safety data show the polymer is well tolerated for most skin types with only rare irritation or pore-clogging issues. As with any new cosmetic ingredient a simple patch test before full use is a smart extra step.

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