Ingredient review
Polysilicone-18 Stearate
INCI: POLYSILICONE-18 STEARATE
A gentle silicone that helps products glide on smoothly and stay put without clogging pores or causing irritation.
In plain English
Polysilicone-18 Stearate is a man-made ingredient that belongs to the silicone family. In cosmetics, it forms a thin, flexible film on the skin that helps other ingredients spread evenly and stay in place longer. It also gives a silky, non-greasy feel and can help products resist water or sweat. Because it sits on top of the skin rather than sinking in, it is generally non-irritating and unlikely to clog pores.
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
Polysilicone-18 Stearate 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 Polysilicone-18 Stearate.
- 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
A synthetic silicone polymer combined with stearic acid (a fatty acid). It is designed to create a smooth, water-resistant film on the skin or hair.
How it works
When applied, the silicone chains spread into a uniform layer that dries to a flexible, breathable film. This film helps lock in other ingredients, reduces friction (so makeup glides on), and provides a barrier that slows water loss from the skin.
Pros
Smooth, silky feel
Polysilicone-18 Stearate gives products a luxurious, non-greasy texture that glides onto skin easily.
Improves wear time
Its film-forming ability helps makeup and sunscreen resist water, sweat, and transfer, so you need fewer touch-ups.
Cons and cautions
Environmental persistence
Like many silicones, this ingredient does not break down easily in nature, which raises concerns about long-term environmental accumulation.
May feel heavy for some
In high concentrations, the film can feel slightly occlusive or heavy, which might not suit very oily or acne-prone skin types.
Best for
- Anyone looking for a long-wearing, water-resistant foundation or sunscreen
- People with normal to dry skin who enjoy a silky, smooth finish
Use caution if
- Those who strictly avoid silicones due to environmental concerns or personal preference
Usage tips
Safety summary
Polysilicone-18 Stearate has a low irritation and comedogenic risk. It is considered safe for use in cosmetics at typical concentrations. As with any ingredient, patch test if you have very sensitive skin.
Research notes
There is limited peer-reviewed research specifically on Polysilicone-18 Stearate, but it is structurally similar to other well-studied silicone film-formers that are widely regarded as safe and non-irritating in cosmetic use.
Common label clues
- Typical concentration
- Typically 1–5% in leave-on products
- Regulatory status
- Approved for use in cosmetics in the US, EU, and many other regions. The Cosmetic Ingredient Review (CIR) panel has evaluated similar silicone polymers and found them safe at typical use levels.
- Common uses
- Foundations, Sunscreens, Primers, Long-wear makeup, Water-resistant skincare
- Environmental note
- Silicones like this one are not readily biodegradable and may persist in water systems. Some brands are moving toward bio-based alternatives to reduce environmental impact.
Good to know
- Polysilicone-18 Stearate is often used in 'long-wear' and 'waterproof' formulas because of its strong film-forming ability.
- It is considered safe by major regulatory bodies when used as directed in cosmetics.
Common questions
What is Polysilicone-18 Stearate in beauty products?
Polysilicone-18 Stearate is a man-made ingredient that belongs to the silicone family. In cosmetics, it forms a thin, flexible film on the skin that helps other ingredients spread evenly and stay in place longer. It also gives a silky, non-greasy feel and can help products resist water or sweat. Because it sits on top of the skin rather than sinking in, it is generally non-irritating and unlikely to clog pores.
What does Polysilicone-18 Stearate do in a beauty product?
When applied, the silicone chains spread into a uniform layer that dries to a flexible, breathable film. This film helps lock in other ingredients, reduces friction (so makeup glides on), and provides a barrier that slows water loss from the skin.
Is Polysilicone-18 Stearate safe for most people?
Polysilicone-18 Stearate has a low irritation and comedogenic risk. It is considered safe for use in cosmetics at typical concentrations. As with any ingredient, patch test if you have very sensitive skin.
Who should be careful with Polysilicone-18 Stearate?
Those who strictly avoid silicones due to environmental concerns or personal preference
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.