What Is Quaternium-18 Bentonite?
Quaternium-18 Bentonite is a blend of two things: bentonite clay and a quaternary ammonium conditioning agent made from hydrogenated tallow. Bentonite is a natural, fine-grained clay formed from volcanic ash while the quaternary ammonium part is a positively charged surfactant often used in hair care. When chemists combine the two, the clay layers are coated with the conditioning agent, turning a dry powder into a soft, cream-like substance that swells in water and certain oils. This modification lets the clay disperse smoothly in creams, lotions and gels.
The cosmetic industry started using organo-clays like Quaternium-18 Bentonite in the late 1960s after researchers discovered that swapping the clay’s natural sodium ions with quaternary ammonium ions improved texture and stability. The process involves blending purified bentonite with a heated solution of the quaternary compound, then drying and milling the mixture into a fine powder.
You will most often see Quaternium-18 Bentonite in masks, cream and gel moisturizers, sunscreens, liquid foundations, hair conditioners and styling products. Brands add it to formulas that need a silky glide or a thicker, cushy feel without making the product heavy or greasy.
Quaternium-18 Bentonite’s Cosmetic Benefits/Uses
In beauty formulas Quaternium-18 Bentonite serves one main purpose: it controls viscosity. By swelling and forming a gentle network throughout a product it thickens watery mixtures, stabilizes emulsions so oil and water stay blended and suspends pigments or exfoliating grains so they do not sink to the bottom. This results in creams and gels that spread evenly, feel luxurious and stay fresh longer.
Who Can Use Quaternium-18 Bentonite
Quaternium-18 Bentonite is generally well tolerated by most skin types. Its clay portion helps mop up excess oil while the conditioning agent keeps the formula from feeling chalky, so normal, combination and oily complexions usually like it. People with very dry or easily irritated skin can still use it, but they may want to pair it with richer moisturizers because clays can draw out surface moisture.
Vegans and vegetarians should know the quaternary ammonium part of this ingredient is made from hydrogenated tallow, a substance traditionally sourced from animal fat. Unless a brand specifies a plant-based alternative, products with Quaternium-18 Bentonite are not considered vegan or vegetarian friendly.
Current safety data show no special restrictions for pregnant or breastfeeding women. The ingredient sits on the skin or hair and is not known to absorb systemically in meaningful amounts. Still, this is not medical advice and anyone who is expecting or nursing should run new products past their doctor to be safe.
The ingredient does not make skin more sensitive to sunlight and it does not interfere with sunscreen filters, so no extra sun precautions are required beyond routine daily SPF.
Potential Side Effects/Adverse Reactions
Responses to topical Quaternium-18 Bentonite vary from person to person. The points below outline potential side effects, but most users will not experience them when the ingredient is used correctly in a well-formulated product.
Skin irritation – A small number of people may notice redness, itching or a stinging feeling after application, especially if their skin barrier is already compromised.
Contact dermatitis – Rare allergic reactions can lead to localized swelling, rash or hives.
Eye irritation – If the product accidentally gets into the eyes it can cause watering or a gritty sensation until rinsed out thoroughly.
Build-up on hair – In leave-in conditioners styling products that contain high levels of the ingredient, some users report a waxy feel that calls for a clarifying shampoo.
If any of these effects occur stop using the product and consult a healthcare professional or dermatologist.
Comedogenic Rating
Rating: 1 out of 5. Quaternium-18 Bentonite is mostly made of absorbent clay that helps soak up excess sebum instead of clogging pores. The quaternary ammonium coating adds a light conditioning layer but does not form a greasy film, so the overall risk of blocked pores is very low. People who are prone to acne can usually use products with this ingredient without seeing extra breakouts. Formulation still matters, though, so heavier creams that pair it with rich oils could raise the chance of congestion.
Summary
Quaternium-18 Bentonite thickens, stabilizes and suspends particles in cosmetic formulas by swelling into a gel network that holds water, oil and pigments in place. This single role improves texture, prevents separation and gives creams and gels a smooth cushy glide. It shows up most in masks, sunscreens, liquid makeup and some hair products but it is not a headline ingredient, so you may not spot it on every label.
Current research and long use in cosmetics point to a strong safety profile with only rare reports of irritation or allergy. As with any new skincare or haircare item, patch test first to make sure your skin agrees with the full formula.