What Is Polyurea Crosspolymer-4?
Polyurea Crosspolymer-4 is a synthetic film-forming polymer created by reacting 1,3-propanediol 2-ethyl-2-(hydroxymethyl)- with bis(isocyanatomethyl)benzene and 1,2-propanediamine. These building blocks link together into a three-dimensional network that gives the ingredient its distinctive flexible yet durable structure. The material does not occur in nature; it is produced in controlled factory settings where temperature, pressure and pH are carefully monitored to get a uniform polymer with cosmetic-grade purity.
The technology behind polyurea chemistry first gained attention in industrial coatings because of its toughness and rapid curing. Formulators later noticed that a finely ground version could deliver similar protective properties on skin without a heavy feel. By the early 2000s suppliers began adapting the process for personal care, refining particle size and removing impurities to meet cosmetic safety standards.
Production starts with mixing the diol, aromatic di-isocyanate and diamine in a solvent-free or low-solvent system. As the reaction proceeds the components join together, forming long chains that further crosslink into a microscopic matrix. After curing, the solid polymer is milled into a light powder that disperses easily in both water-based and oil-based formulas.
Because it forms an invisible, flexible film, Polyurea Crosspolymer-4 is found in primers, long-wear foundations, tinted moisturizers, setting sprays, sheet masks, peel-off masks, anti-aging serums, sunscreens and hair styling products where humidity resistance and smooth texture are valued.
Polyurea Crosspolymer-4’s Cosmetic Benefits/Uses
Its role in beauty products centers on a single yet versatile function.
Film forming: Once applied to skin or hair, the polymer dries into a thin breathable layer that helps lock in active ingredients, extend wear time, reduce transfer, improve water or sweat resistance and create a smoother surface for makeup application.
Who Can Use Polyurea Crosspolymer-4
This film former is generally suitable for all skin types including oily, dry, combination and mature skin because it sits on the surface rather than penetrating deeply. Sensitive or eczema-prone skin usually tolerates it as the polymer is chemically inert, though anyone with a history of reactions to synthetic resins should stay alert for irritation.
The ingredient is produced entirely from petroleum-derived feedstocks with no animal inputs, making it appropriate for vegans and vegetarians.
Current safety data show no systemic absorption, so products containing Polyurea Crosspolymer-4 are not expected to pose a risk during pregnancy or while breastfeeding. This is not medical advice and pregnant or nursing individuals should still review any skincare product with their physician to be safe.
Polyurea Crosspolymer-4 does not cause photosensitivity and can be used alongside daytime sunscreens. It has no known incompatibilities with common cosmetic actives, preservatives or makeup pigments, though its film can slightly slow the evaporation of volatile ingredients which may intensify fragrances for a short time after application.
Potential Side Effects/Adverse Reactions
Responses to topical Polyurea Crosspolymer-4 vary from person to person. The following list covers potential side effects but these are uncommon when the ingredient is formulated and used correctly.
- Mild skin irritation such as redness stinging or itching on very reactive skin
- Contact dermatitis in individuals already sensitized to isocyanate-based polymers
- Temporary clogged pores if very thick layers are applied on acne-prone areas
- Eye irritation if loose powder or product runoff enters the eyes
- Build-up on hair shafts leading to dullness or stiffness if not cleansed thoroughly
If any of these effects occur stop using the product and consult a healthcare professional or dermatologist.
Comedogenic Rating
Rating: 1/5
Polyurea Crosspolymer-4 is considered low on the comedogenic scale because it is a large, inert film-forming particle that tends to sit on top of skin rather than seeping into pores. Its breathable matrix lets water vapor pass while resisting oil migration, reducing the chance of pore blockage. That said, very thick layers or pairing it with heavy oils can trap sebum underneath which is why a small number of users report temporary congestion.
With normal use it is generally suitable for acne-prone or breakout-prone skin.
The final product formula plays a role too: lightweight gels or sprays pose minimal risk, while dense creams loaded with waxes may feel heavier and increase the chance of clogged pores.
Summary
Polyurea Crosspolymer-4 is a synthetic film former that dries into a flexible, invisible layer. This film helps lock actives on the surface, boosts water and sweat resistance, smooths texture for makeup and extends wear time. Because the polymer is inert and remains on the skin’s surface, it shows very low irritation and almost no systemic absorption.
Although not as widespread as silicone resins, it is gaining popularity in long-wear foundations, primers and transfer-resistant skincare where a lightweight yet durable finish is prized.
Current safety data rate the ingredient as low risk for irritation or toxicity. Still, everyone’s skin is unique so it is smart to patch test any new product containing Polyurea Crosspolymer-4 before full-face or daily use.