Ingredient review
Polyurethane-45
INCI: POLYURETHANE-45
Polyurethane-45 is a synthetic film-former that helps makeup last longer and resist water, but it may feel heavy on some skin types.
In plain English
Polyurethane-45 is a man-made polymer that forms a thin, flexible film on your skin or hair. Think of it like a clear, breathable plastic wrap that helps makeup stay put, keeps sunscreen from washing off, or holds a hairstyle in place. It's designed to be water-resistant and durable, but it can sometimes feel a bit tight or heavy, especially if you have dry or sensitive skin.
Review score
Safety, usefulness, and evidence
Potentially useful with some tradeoffs
The evidence base is useful, but some claims depend heavily on the formula.
Risk flags are low for most users, though the finished product can still irritate.
- Source
- synthetic
- Evidence
- moderate
- Irritation
- low
- Clogging risk
- low
Quick decision guide
Useful, but context matters
Polyurethane-45 is generally a lower-concern ingredient when the full formula suits your skin.
Plain-English read
Treat this as a practical screening step before you compare products that contain this ingredient.
- Step 1Start with the score, then check the irritation and clogging risk before judging Polyurethane-45.
- Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
- Step 3If a product stings, breaks you out, or worsens irritation, judge the finished formula and stop using it even if the ingredient scores well.
Score terms in plain English
Irritation risk
lowLess likely to sting, burn, or bother most users, though sensitive skin can still react.
Clogging risk
lowLess likely to feel heavy or contribute to clogged pores for most skin types.
Evidence level
moderateThere is useful support, but formula details and claim strength still matter.
What it is
Polyurethane-45 is a synthetic polymer belonging to the polyurethane family. In cosmetics, it is used as a film-forming agent, meaning it creates a continuous layer on the skin or hair after the product dries. This helps improve the wear time, water resistance, and texture of formulations.
How it works
When applied, the water or solvent in the product evaporates, leaving behind a thin, flexible film of polyurethane-45. This film adheres to the surface, creating a barrier that resists water, sweat, and friction. In makeup, it helps pigments stay in place; in sunscreens, it helps the UV filters remain effective longer; in hair products, it provides hold without stiffness.
Pros
Excellent staying power
Helps makeup and sunscreen resist water, sweat, and rubbing, so you don't have to reapply as often.
Flexible film
Unlike some older film-formers, polyurethane-45 creates a flexible layer that moves with your skin, reducing cracking or flaking.
Cons and cautions
Can feel heavy
On dry or sensitive skin, the film may feel tight, sticky, or like a mask, especially in high concentrations.
Requires double cleansing
Because it's water-resistant, you'll likely need an oil-based cleanser or micellar water to fully remove it, which can be inconvenient.
Best for
- People who want long-lasting, waterproof makeup
- Those who need sunscreen that stays on during swimming or sweating
Use caution if
- Individuals with very dry or sensitive skin who find film-formers uncomfortable
- Anyone who prefers minimal, easily removable products
Usage tips
Safety summary
Polyurethane-45 is considered safe for use in cosmetics at typical concentrations. It has a low risk of irritation and is rarely allergenic. However, its film-forming nature can be uncomfortable for some, and it requires thorough removal to avoid buildup.
Research notes
Research on polyurethane-45 specifically is limited, but the broader class of polyurethane film-formers is well-studied and widely used in cosmetics. Safety assessments by industry panels have found them to be safe for topical use. No significant health concerns have been identified.
Common label clues
- Typical concentration
- 1% to 10%
- Regulatory status
- Approved for use in cosmetics in the US, EU, and many other regions. No specific concentration limits are set, but it is generally recognized as safe when used as intended.
- Common uses
- Long-wear foundations, Waterproof mascaras, Sunscreens, Hair styling products
- Environmental note
- As a synthetic polymer, polyurethane-45 is not biodegradable. Its environmental impact depends on how it is formulated and disposed of, but it is not known to be a major pollutant.
Good to know
- Polyurethane-45 is often used in combination with other film-formers to fine-tune texture and durability.
- It is considered non-comedogenic for most people, but individual reactions can vary.
Common questions
What is Polyurethane-45 in beauty products?
Polyurethane-45 is a man-made polymer that forms a thin, flexible film on your skin or hair. Think of it like a clear, breathable plastic wrap that helps makeup stay put, keeps sunscreen from washing off, or holds a hairstyle in place. It's designed to be water-resistant and durable, but it can sometimes feel a bit tight or heavy, especially if you have dry or sensitive skin.
What does Polyurethane-45 do in a beauty product?
When applied, the water or solvent in the product evaporates, leaving behind a thin, flexible film of polyurethane-45. This film adheres to the surface, creating a barrier that resists water, sweat, and friction. In makeup, it helps pigments stay in place; in sunscreens, it helps the UV filters remain effective longer; in hair products, it provides hold without stiffness.
Is Polyurethane-45 safe for most people?
Polyurethane-45 is considered safe for use in cosmetics at typical concentrations. It has a low risk of irritation and is rarely allergenic. However, its film-forming nature can be uncomfortable for some, and it requires thorough removal to avoid buildup.
Who should be careful with Polyurethane-45?
Individuals with very dry or sensitive skin who find film-formers uncomfortable Anyone who prefers minimal, easily removable products
Research sources
Ingredient reviews are educational and are not medical advice. Patch test new products and ask a licensed clinician about persistent irritation, allergies, pregnancy-specific questions, or diagnosed skin conditions.