pediaBentonite clay is a natural smectite clay composed predominantly of montmorillonite mineral and derived from volcanic ash. Known for its high adsorption and water absorption capacity, bentonite is widely used in cosmetic formulations as an absorbent, viscosity enhancer, and colorant. Among 4500+ known minerals, only approximately 30 are used in the cosmetic and pharmaceutical industries—bentonite is among the most widely used. The CIR (Cosmetic Ingredient Review) Expert Panel has assessed bentonite as safe for cosmetic use.
This article is not a product promotion. Its purpose is to provide an independent framework regarding bentonite clay's position in scientific literature.
Mineralogical structure and origin
Bentonite is a colloidal and plastic clay composed predominantly of montmorillonite mineral. It takes its name from the area near Fort Benton, Wyoming, where it was first discovered in 1898. It is formed by the in-situ weathering (devitrification) of volcanic glass (ash) and is generally extracted by opencast mining methods.
The smectite family and montmorillonite
Montmorillonite is the most common member of the smectite group of clay minerals. It has a layered silicate structure; an alumina octahedra layer is positioned between two silica tetrahedral layers (2:1 structure). The interlayer spaces of these layers are the source of bentonite's extraordinary water and molecule absorption capacity—it can absorb several times its dry weight in water and expands significantly during this process. The terms "bentonite" and "montmorillonite" are sometimes used interchangeably in the literature.
Bentonite in Turkey
Turkey possesses significant bentonite deposits among the world's major bentonite-producing countries. According to CIR reports, bentonite is commercially extracted in Australia, China, France, India, Russia, Senegal, South Africa, Spain, Turkey, and the USA. Raw clay extracted undergoes crushing, drying, classification, and grinding processes before becoming suitable for cosmetic use.
Physical properties and absorption mechanism
Adsorption and absorption capacity
Bentonite clay possesses both adsorption (surface adhesion) and absorption (internal uptake) capacity. Due to its layered structure, surface negative charges, and expandable interlayer spaces, it can effectively attract oils, dirt, and other organic molecules. This property forms the foundation for its use in cosmetic products in the context of "cleansing" and "purification".
pH and skin compatibility
Bentonite used for cosmetic purposes must be compatible with the pH of the application site. Fine granulometry (particle size) and low toxicity are prerequisites for cosmetic use. According to CIR data, the D50 particle size reported for cosmetic-grade bentonite is 61.1 µm.
Cosmetic use and scientific evaluation
Functions and applications
Bentonite clay is used in various functions in cosmetic formulations: absorbent, viscosity enhancer (texture modifier), opacifying agent, and colorant. In EU regulations, it is listed in Annex IV (permitted colorants) as CI 77004. Primary applications include: facial masks (clay masks), foundations, skin care preparations, sun protection products, and soaps.
CIR safety assessment (2000/2023)
The CIR Expert Panel first evaluated bentonite and other clay components in 2000, and conducted a comprehensive review process between 2018-2023. In both evaluations, bentonite was approved as safe for cosmetic use. According to VCRP data (2022), bentonite was reported in 262 cosmetic formulations total—a significant increase compared to 94 uses in 1998. Slightly more than half of these uses are in leave-on products.
Concentration limits
According to CIR data, bentonite has been reported in cosmetic products at the following concentrations: up to 15% in skin care preparations (leave-on), up to 8% in face and neck formulations, up to 8% in foundations, up to 5% in bath soaps, and up to 4% in paste masks (mud packs).
Dermal safety tests
Comprehensive dermal safety testing has been conducted. In HRIPT (Human Repeated Insult Patch Test) studies: a foot mask containing 3.5% bentonite, a clay mask containing 3.8% bentonite (108 subjects), a facial cream containing 7.5% bentonite, a lip product containing 14.5% kaolin, and a clay mask containing 40% kaolin showed no dermal sensitization. In diffusion cell studies, trace heavy metals in clay preparations were found not to penetrate the skin after 24 hours (CIR, 2023).
Safety profile
Heavy metal contamination: what is known?
Natural clay minerals may contain trace amounts of heavy metals (including lead) depending on their source. This issue is also emphasized by the EWG (Environmental Working Group). However, diffusion cell studies in the CIR report demonstrated that these trace metals do not penetrate human skin. Bentonite used for cosmetic purposes must undergo purification processes complying with pharmacopeial specifications; chemical purity, microbiological cleanliness, and particle size testing are mandatory.
EU and international regulations
Under European Union cosmetics regulations (EC/1223/2009), bentonite is listed in Annex IV as CI 77004 among permitted colorants—defined as "natural hydrated aluminum silicate". The SCCS (Scientific Committee on Consumer Safety) examined bentonite, hectorite, and kaolin when assessing the safety of aluminum compounds in cosmetic products. In the USA, bentonite is classified by the FDA as GRAS (Generally Recognized as Safe) (21 CFR§182.1155).
Bentonite clay in soap making
Addition timing and method
Bentonite clay is typically added at trace stage in cold-process soap making. Preparing a dispersion with a small amount of water (slurry) and mixing it with the soap batter ensures more homogeneous distribution. Some soap makers prefer adding the clay to the oil phase.
Usage ratio
Generally, it is used at approximately 1-3% of the total oil amount (approximately 1-2 teaspoons per 500 grams of oil). Higher ratios may increase the soap's drying effect and give it a matte appearance.
Properties it imparts to soap
Bentonite clay provides two primary contributions to soap: a "textured" cleansing feel through its approach to absorbing excess surface oil, and increased hardness of the soap. When used together with activated charcoal, it creates a synergistic texture that enhances the soap's cleansing character. It also facilitates removal from molds and can enhance the "slip" of lather.
Frequently asked questions
What is bentonite clay?
Bentonite is a natural smectite clay derived from volcanic ash, composed predominantly of montmorillonite mineral. It is known for its high water absorption capacity and adsorption properties.
What is bentonite clay used for in cosmetics?
In cosmetic formulations, it is used as an absorbent, viscosity enhancer, and colorant. It is particularly preferred in facial masks and cleansing products for its ability to draw excess oil and impurities from the skin surface.
Is bentonite clay safe?
The CIR Expert Panel has assessed bentonite as safe for cosmetic use. In the USA, it has GRAS classification by the FDA. Comprehensive HRIPT testing showed no dermal sensitization.
Why is bentonite clay used in soap?
In soap making, it provides a textured cleansing feel through its approach to absorbing excess oil, increases the soap's hardness, and facilitates removal from molds.
Chailea products containing this ingredient
- Natural Activated Charcoal Soap 100 g
References
1. CIR Expert Panel (2023). Amended Safety Assessment of Naturally-Sourced Clays as Used in Cosmetics. Cosmetic Ingredient Review. CIR Report
2. Cosmetics (MDPI) (2024). The Scenario of Clays and Clay Minerals Use in Cosmetics/Dermocosmetics. Cosmetics, 11(1), 7. doi:10.3390/cosmetics11010007
3. CIR Expert Panel (2000). Final Report on the Safety Assessment of Bentonite, Kaolin, and related clay ingredients. International Journal of Toxicology.