Ingredient review
Quaternium-18 Bentonite
INCI: QUATERNIUM-18 BENTONITE
A safe, modified clay that improves product texture and stability without major skin concerns.
In plain English
Quaternium-18 Bentonite is a clay mineral that has been treated with a quaternary ammonium compound to make it more compatible with oils and waxes. In cosmetics, it acts as a thickener and helps keep ingredients evenly mixed. It gives products a smooth, creamy feel and prevents separation. It is not absorbed into the skin and sits on the surface, so it is generally non-irritating and non-comedogenic.
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
- semi synthetic
- Evidence
- moderate
- Irritation
- low
- Clogging risk
- low
Quick decision guide
Useful, but context matters
Quaternium-18 Bentonite 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 Quaternium-18 Bentonite.
- 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 chemically modified bentonite clay where the surface has been coated with quaternium-18, a quaternary ammonium salt. This modification makes the normally water-loving clay able to swell and thicken oil-based formulas.
How it works
When added to a formula, Quaternium-18 Bentonite absorbs oils and swells, forming a gel-like network. This network increases the viscosity (thickness) of the product and helps suspend solid particles like pigments or powders, preventing them from settling. It also stabilizes emulsions by reinforcing the oil-water interface.
Pros
Improves texture
Creates a smooth, creamy feel in foundations and lipsticks, making application easier and more pleasant.
Prevents separation
Helps keep pigments and powders evenly suspended, so you don't have to shake or stir your product before use.
Cons and cautions
Not a skin active
It only affects product feel and stability, not skin health or appearance.
Potential drying feel
In high concentrations, it can leave a slightly powdery or dry finish, which may not suit very dry skin types.
Best for
- Anyone using color cosmetics like foundation or mascara
- People who prefer stable, non-separating formulas
Use caution if
- Those with extremely dry skin may find formulas with high clay content slightly drying
Usage tips
Safety summary
Quaternium-18 Bentonite is considered safe for use in cosmetics. It is not absorbed through the skin, has low irritation potential, and is non-comedogenic. The Cosmetic Ingredient Review (CIR) panel has reviewed similar modified clays and found them safe as used.
Research notes
Research on Quaternium-18 Bentonite specifically is limited, but it is chemically similar to other modified clays (e.g., Quaternium-18 Hectorite) that have been reviewed by the CIR and found safe. Its primary function is as a thickener and stabilizer, not a bioactive ingredient.
Common label clues
- Typical concentration
- 0.5% to 5%
- Regulatory status
- Approved for use in cosmetics by the FDA and EU CosIng database. No concentration restrictions are specified, but typical use is low.
- Common uses
- Foundations, Mascaras, Lipsticks, Creams, Lotions
- Environmental note
- Bentonite is a naturally occurring clay mined from the earth. The modification process uses quaternary ammonium compounds, which are synthetic. Environmental impact is considered low due to small usage amounts.
Good to know
- It is often used in 'oil-control' or 'matte' products because it can absorb excess oil.
- The quaternary ammonium treatment makes it more compatible with silicones and oils than raw bentonite clay.
Common questions
What is Quaternium-18 Bentonite in beauty products?
Quaternium-18 Bentonite is a clay mineral that has been treated with a quaternary ammonium compound to make it more compatible with oils and waxes. In cosmetics, it acts as a thickener and helps keep ingredients evenly mixed. It gives products a smooth, creamy feel and prevents separation. It is not absorbed into the skin and sits on the surface, so it is generally non-irritating and non-comedogenic.
What does Quaternium-18 Bentonite do in a beauty product?
When added to a formula, Quaternium-18 Bentonite absorbs oils and swells, forming a gel-like network. This network increases the viscosity (thickness) of the product and helps suspend solid particles like pigments or powders, preventing them from settling. It also stabilizes emulsions by reinforcing the oil-water interface.
Is Quaternium-18 Bentonite safe for most people?
Quaternium-18 Bentonite is considered safe for use in cosmetics. It is not absorbed through the skin, has low irritation potential, and is non-comedogenic. The Cosmetic Ingredient Review (CIR) panel has reviewed similar modified clays and found them safe as used.
Who should be careful with Quaternium-18 Bentonite?
Those with extremely dry skin may find formulas with high clay content slightly drying
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.