Ingredient review
C24-28 Alkyl Dimethyl Siloxy Trimethylsiloxysilicate
INCI: C24-28 ALKYLDIMETHYLSILOXY TRIMETHYLSILOXYSILICATE
A silicone film-former that helps products stay put and resist water, but may feel heavy on oily or acne-prone skin.
In plain English
This is a type of silicone wax that creates a thin, flexible film on your skin or hair. It helps makeup last longer, prevents sunscreen from washing off, and gives a smooth, silky feel. Because it's a larger molecule, it sits mostly on the surface and doesn't penetrate deeply, which makes it generally non-irritating. However, it can feel a bit heavy or greasy for people with very oily 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
C24-28 Alkyl Dimethyl Siloxy Trimethylsiloxysilicate 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 C24-28 Alkyl Dimethyl Siloxy Trimethylsiloxysilicate.
- 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 with long alkyl chains (C24-28) that gives it wax-like properties. It is designed to form a water-resistant, flexible film on skin or hair.
How it works
When applied, the molecules spread into a thin, even layer that dries down to a flexible, water-repellent film. This film helps lock in other ingredients, prevents makeup from smudging or fading, and improves the spreadability and feel of the product.
Pros
Long-lasting wear
Helps makeup and sunscreen stay put for hours, even in humidity or water exposure.
Smooth application
Gives a silky, even finish that makes products glide on easily and feel comfortable.
Cons and cautions
Can feel heavy
On oily or combination skin, the film may feel greasy or clogging, especially in high concentrations.
Hard to remove
Requires an oil-based or double-cleansing routine to fully remove, or it may build up on skin.
Best for
- People who want long-wearing makeup
- Those who need water-resistant sunscreen
- Anyone with dry or normal skin looking for a smooth finish
Use caution if
- People with very oily or acne-prone skin who prefer lightweight, non-silicone formulas
- Those who avoid silicones for personal or environmental reasons
Usage tips
Safety summary
Generally recognized as safe for topical use in cosmetics. Low irritation and allergy potential. No known health risks at typical concentrations.
Research notes
Safety assessments by the Cosmetic Ingredient Review (CIR) panel have concluded that alkyl silicones are safe as used in cosmetics. Most evidence comes from industry studies and regulatory reviews rather than independent clinical trials.
Common label clues
- Typical concentration
- 1% to 10%
- Regulatory status
- Approved for use in cosmetics in the US, EU, and many other regions. No known restrictions at typical use levels.
- Common uses
- Long-wear foundations, Waterproof mascaras, Sunscreens, Lip products, Primers
- Environmental note
- Silicones like this one are not readily biodegradable and can accumulate in the environment. Some brands are moving toward biodegradable alternatives.
Good to know
- This ingredient is often used in 'transfer-proof' or '24-hour wear' makeup.
- It is considered safe by cosmetic safety panels, but its environmental impact is a concern because it is not biodegradable.
Common questions
What is C24-28 Alkyl Dimethyl Siloxy Trimethylsiloxysilicate in beauty products?
This is a type of silicone wax that creates a thin, flexible film on your skin or hair. It helps makeup last longer, prevents sunscreen from washing off, and gives a smooth, silky feel. Because it's a larger molecule, it sits mostly on the surface and doesn't penetrate deeply, which makes it generally non-irritating. However, it can feel a bit heavy or greasy for people with very oily skin.
What does C24-28 Alkyl Dimethyl Siloxy Trimethylsiloxysilicate do in a beauty product?
When applied, the molecules spread into a thin, even layer that dries down to a flexible, water-repellent film. This film helps lock in other ingredients, prevents makeup from smudging or fading, and improves the spreadability and feel of the product.
Is C24-28 Alkyl Dimethyl Siloxy Trimethylsiloxysilicate safe for most people?
Generally recognized as safe for topical use in cosmetics. Low irritation and allergy potential. No known health risks at typical concentrations.
Who should be careful with C24-28 Alkyl Dimethyl Siloxy Trimethylsiloxysilicate?
People with very oily or acne-prone skin who prefer lightweight, non-silicone formulas Those who avoid silicones for personal or environmental reasons
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.