Porecelain

Flawless skin starts with the fine print.

Bentonite

Bentonite is rated Clear, and the 0 behind that rating is a real measurement of the material the label names — which is not a sentence this site gets to write often. What the charts leave out is how thin the record is underneath it. Fulton graded bentonite once, in 1989, in a rabbit's ear. That is one investigator, one reading, and a material whose composition varies with the deposit it was dug out of.

Clear Low confidence Legacy score 0 on a 0-5 scale · Fulton 1989 · low reliability

Fulton 1989 rabbit ear 0 of 5, in one carrier; no second reading we can find.

What it is

A mined clay. The Cosmetic Ingredient Review's 2023 final amended report on naturally-sourced clays records that the principal constituent of bentonite is montmorillonite, that other minerals such as illite, kaolinite and non-clay detrital minerals can be present though rarely above about 10%, and that montmorillonite compositions "frequently vary either in its lattice structure or in the exchangeable ions present". It gives a typical mineral composition in oxide terms — silicon, aluminium, sodium and iron oxides, with smaller fractions of magnesium, calcium and potassium — but we do not reproduce the percentages: as printed in the copy we read they sum to more than 100%, and we cannot tell which figure is wrong. It records a supplier's account of the material as mined ore that is washed, filtered, dried, treated and tested. The US Geological Survey describes bentonite as beds containing smectite-group clay minerals including montmorillonite, and says those beds "usually form from altered volcanic ash", though other rocks can serve as sources. In cosmetics it does powder and thickener jobs. CIR reports that all eight of the naturally-sourced clays it assessed, bentonite included, function as absorbents and bulking agents, with other functions also reported. On a label it is Bentonite, sometimes written Bentonite Clay.

Why we rate it Clear

We rate it Clear at Low confidence. Low because the numeric evidence is a rabbit-ear grade from one investigator, which is the tier that gets Low here whichever way it points. The row, and it is the right row. Fulton's 1989 survey in the Journal of the Society of Cosmetic Chemists prints "Bentonite" in Table I at a comedogenicity grade of 0 on a 0–5 scale, with no asterisk and no range. We read that off our own 400dpi transcription of the table rather than a chart quoting it. The name printed in the paper is the name the score is quoted under, with nothing dropped from it and no derivative standing in for the parent material — on this site that is the exception rather than the rule. The match is at the level of the name and no further: no deposit, no mineralogy, no activation, no particle size, no surface treatment, no supplier and no grade is reported anywhere in the paper. Its neighbours matter as much as its number. Table I groups its rows by kind, and bentonite sits among the powders and thickening agents, between carbomer 940 and kaolin, alongside magnesium aluminum silicate 0, kaolin 0, talc 1 and PVP 0. Bentonite's row carries no asterisk, and nor do those neighbours. The asterisk belongs to the oils, printed as "VI. Oils*", where Fulton's footnote defines it as "Results depend on source of raw material" — the caveat that governs every oil and butter row in the paper does not formally reach this one. Whether it ought to is a separate question, and it is in the limits below. Fulton's own grade key, published on p. 322 and rarely quoted beside his numbers, reads "a minimal grade of 0 to 1 is not considered significant. Grade 2 to 3 is borderline. However, a grade of 4 to 5 is uniformally reproduceable and considered positive." A 0 is as low as that scale goes. What is not there. Fulton's earlier paper with Pay and Fulton, in the Journal of the American Academy of Dermatology in 1984, ran the same model on the same 0–5 scale over therapeutic products, cosmetics and ingredients — and it has no bentonite row at all. Its nearest entries are "Kaolin*" at 1 and "Hectorite*" at 1, both under that paper's own footnote, which reads that materials so marked "were either diluted with mineral oil or incorporated into an alcohol gel at a 10% concentration". Hectorite is a smectite clay like bentonite and it is not bentonite, so its 1 stays where it is. That paper's threshold is drawn in a different place too — "a minimal grade of 1 to 2 is not considered significant", with 3 or above positive — so its digits do not read across to the 1989 table. Kaolin was therefore graded twice by Fulton and bentonite once. Nor does the rest of the corpus we hold add a second reading. Morris and Kwan's 1983 rabbit-ear paper, the independent assay on the same scale from a different laboratory, has 32 rows covering lanolins, vegetable oils, esters and surfactants, and no minerals at all. The abstract of Nguyen, Dang and Maibach's 2007 rabbit study names its fourteen test materials; bentonite is not among them.

What the evidence doesn’t tell you

One rabbit-ear reading from one investigator is what the number on this page rests on, and Fulton undercut that model himself. He wrote that "not everything that irritates this model will also irritate human skin", and closed the paper by calling the survey "not at all definitive but simply designed to stimulate research". Those cautions apply to a 0 exactly as hard as to anyone's 4. A low grade from a test its author called non-definitive is a low grade from a test its author called non-definitive. The paper does not say which bentonite. No deposit, no grade, no purity, no particle size, no supplier — the row carries a name and a digit. Bentonite is a mined rock whose principal mineral varies "either in its lattice structure or in the exchangeable ions present", by CIR's own description, and which can carry up to about 10% of other minerals. One row fixes none of that. The asterisk Fulton attached to the oils section, for results that depend on the source of the raw material, is not attached here. An absent asterisk is not evidence that this material does not vary with its source; it records only that Fulton did not mark the row. Concentration and vehicle are both open. The method was the ingredient at roughly 10% in propylene glycol, 1 ml applied to the inner ear of three New Zealand albino rabbits, five days a week for two weeks, follicular keratosis measured with a micrometer. The paper does show, in Table II, that the carrier moves a grade: one pigment, D&C red #36, comes out at 3 in mineral oil, 2 in pentaerythrital tetra capra/caprylate, 1 in propylene glycol and 0 in PEG 400. That is a pigment rather than a clay, and what changed across those four rows is the vehicle, not the material. We note it because bentonite was graded in one vehicle only. CIR's 2022 concentration survey reports bentonite in leave-on face and neck preparations at up to 8%. What it does at that concentration, or in a carrier that does not evaporate, was not measured. We identified no human comedogenicity study of bentonite. The nearest human evidence is a treatment trial, not a pore test. Salimi and colleagues, in the Journal of Cosmetic Dermatology in 2025, randomised 60 people with moderate acne in Sari, Iran, to a bentonite mask or a placebo, both on top of oral azithromycin, applied nightly for eight weeks; total lesion count fell 55.45% ± 21.74% in the mask arm against 21.74% ± 14.74% on placebo. Four things stop that being a result about bentonite. The mask was bentonite and Alcea sulphurea extract in a 1:1 ratio with corn starch, glycerin, water and sodium benzoate, so no arm isolates the clay. Both arms took an antibiotic. The placebo was a gel and the active was a mask, which the authors list as a limitation because participants could deduce their allocation. And the between-group difference did not survive the paper's own adjusted analysis: the groups differed at baseline in age and education, and after adjusting for both, the between-group p-values are 0.063 for lesion count and 0.203 for the acne severity index. The abstract reports the unadjusted comparison. It is also, at best, evidence about a formula rather than an ingredient. A study often read as pointing the other way does not reach this material either. Choi and colleagues' 2025 case-control study in Clinical, Cosmetic and Investigational Dermatology compared 81 people with acne to 70 without at a Guangzhou hospital and found powder products an independent risk factor after adjustment, odds ratio 3.47 (95% CI 1.58–7.59, p = 0.02). It recorded self-reported product categories rather than ingredients, names none, and being observational shows association rather than cause. Bentonite is a powder used in face products; that is the whole of the connection. We record the study because omitting it would be a choice about which way the page points, not because a category-level questionnaire result carries information about a clay. The mechanism everyone repeats is the part with the least behind it. "Absorbs excess oil, unclogs pores" is the standard sentence, and the 2025 trial prints a version of it — but the references it hangs that sentence on are a mineralogical survey of an Iranian clay deposit, a study of zinc adsorption isotherms in water, a laser-spectroscopy elemental analysis of Fuller's earth and a polyherbal acne soap formulation paper. None of them counted a follicle. That same paper also calls bentonite "also known as Fuller's Earth", which CIR treats as a separate ingredient in the same report. We have found no measurement of what bentonite does to a human follicle, in either direction. Do not read the derivative across to the parent, either. The one clay product with a real FDA-approved human trial behind it is bentoquatam — quaternium-18 bentonite, a chemically modified clay — which Marks and colleagues tested in 1995 as a barrier against urushiol in people allergic to poison ivy and oak. Its endpoint is allergic contact dermatitis. It is a different material, tested for a different thing. Finally, the safety literature is not pore literature. CIR's final amended report of March 2023 concluded that kaolin is safe in the present practices of use and concentration described in that assessment, and that the remaining seven clays, bentonite among them, are safe in present practices of use and concentration "with the exception that the available data are insufficient to make a determination that these ingredients are safe in products that may be incidentally inhaled". That exception is about breathing a powder, not about pores, and a safety conclusion is not a comedogenicity finding in either direction. In the text of that report we read, the words comedogenic, comedone and acne do not appear.

Where you’ll see it

On a label as Bentonite, sometimes Bentonite Clay. CIR's 2023 final amended report gives the only use figures we can cite to a finished document: 221 reported uses in cosmetic products in the 2023 Voluntary Cosmetic Registration Program survey — second only to kaolin among the clays, and up from 94 uses in 1998 — with about half of them in leave-on formulations. The 2022 industry concentration survey it reports puts the maximum leave-on dermal use at 8% in face and neck preparations, behind kaolin's 16%, and lists bentonite at 0.9% in spray suntan products. Two caveats travel with those numbers. The VCRP is a voluntary registration programme, so a use count is a count of what was reported, not a market survey. And a maximum concentration in a category is not a typical one. The familiar places a reader meets this clay — masks, cleansers, powders, mineral makeup — are illustrative categories rather than a measured breakdown, and we have not audited which of those 221 uses fall where.

Sources

Each source says what it actually is. Several widely-cited “sources” for comedogenic ratings are republishing the same 1989 assay, and counting them as independent agreement is how a thin evidence base gets made to look thick.

  1. Fulton JE. "Comedogenicity and irritancy of commonly used ingredients in skin care products." J Soc Cosmet Chem 40:321–333 (1989) The primary source for the 0, and the only document we have found that assigns bentonite a comedogenic grade. Document state, stated plainly because it is mixed: the numeric grade is read from our own 400dpi visual transcription of Table I, while the prose quoted here is read from a full-text scrape of the paper in which most of Table I's numerals are lost to OCR — so no number on this page comes from that scrape. Method as printed: the ingredient at roughly 10% in propylene glycol, 1 ml applied to the inner ear of three New Zealand albino rabbits, five days a week for two weeks, follicular keratosis measured with a micrometer. "Bentonite" has its own row, graded 0, no asterisk and no range, among the powders and thickening agents, in a run of rows carrying no asterisk, unlike "VI. Oils*". The grade key is on p. 322: 0 to 1 "is not considered significant". Table II of the same paper grades one pigment at 3, 2, 1 and 0 across four vehicles. It records no source, grade, particle size or supplier for the bentonite sample, and Fulton calls the whole survey "not at all definitive but simply designed to stimulate research". A single-investigator rabbit survey, not a clinical trial and not a human result.
  2. Fulton JE Jr, Pay SR, Fulton JE III. "Comedogenicity of current therapeutic products, cosmetics, and ingredients in the rabbit ear." J Am Acad Dermatol 10(1):96–105 (1984) The same investigator's earlier rabbit-ear survey, read off a 400dpi render of the journal scan, and cited here for what it does NOT contain: there is no bentonite row in it. Its nearest entries, under "Miscellaneous ingredients", are "Kaolin*" and "Hectorite*", both at 1. Two features belong to this paper alone and must travel with its numbers. Its asterisk is a dilution note, not the 1989 raw-material note — materials so marked "were either diluted with mineral oil or incorporated into an alcohol gel at a 10% concentration". And its key differs: "a minimal grade of 1 to 2 is not considered significant", with 3 or above positive, so the same digit does not mean the same thing in Fulton's two papers. Relevant here as evidence that the 1989 reading of bentonite stands alone even within its own author's work.
  3. Morris WE, Kwan SC. "Use of the rabbit ear model in evaluating the comedogenic potential of cosmetic ingredients." J Soc Cosmet Chem 34:215–225 (1983) An independent primary rabbit-ear assay on the same 0–5 scale, from a different laboratory, six years before Fulton 1989 — the document that would count as corroboration had it tested this material. It did not. Its 32 rows cover seven lanolins, nine vegetable oils, eleven esters and five surfactants, and include no minerals. Cited for that absence, and as the paper that shows such corroboration was possible and did not happen here: on other materials Morris and Kwan openly contradict Fulton and say so in print.
  4. Nguyen SH, Dang TP, Maibach HI. "Comedogenicity in rabbit: some cosmetic ingredients/vehicles." Cutan Ocul Toxicol 26(4):287–292 (2007) The most recent rabbit-ear study in the corpus we hold, graded on a 0–4 scale — a third scale, and one easily misread as Fulton's. We have read its abstract verbatim and not its full text. The abstract names all fourteen test materials, which are esters, fatty alcohols, hydrocarbons, one butter and one surfactant; bentonite is not among them. Cited for that absence.
  5. Cosmetic Ingredient Review (Burnett CL, prepared; Expert Panel for Cosmetic Ingredient Safety). "Amended Safety Assessment of Naturally-Sourced Clays as Used in Cosmetics." Final Amended Report, release date 31 March 2023, panel meeting 6–7 March 2023 An expert-panel SAFETY assessment, and the source of every composition and use figure on this page. Document state checked deliberately, because this project has cited a comment-stage draft as a finished one before: this is the FINAL amended report, not the 2022 "Draft Tentative Amended Report" that preceded it and carried a do-not-quote footer on every page. It assesses eight naturally-sourced clays, six of them re-reviews of the 2003 report, and concludes that kaolin is safe in the present practices of use and concentration described in the assessment, and that the other seven — bentonite included — are safe in present practices of use and concentration "with the exception that the available data are insufficient to make a determination that these ingredients are safe in products that may be incidentally inhaled". That is a safety conclusion about inhalation, not a finding about follicles. In the text we read, the words comedogenic, comedone and acne do not appear. It also assesses Fuller's Earth as an ingredient separate from bentonite.
  6. Cosmetic Ingredient Review. "Final Report on the Safety Assessment of Aluminum Silicate, Calcium Silicate, Magnesium Aluminum Silicate, … Attapulgite, Bentonite, Fuller's Earth, Hectorite, Kaolin, … Montmorillonite, Pyrophyllite, and Zeolite." Int J Toxicol 22(Suppl 1):37–102 (2003) The predecessor safety assessment, finalised by the Panel in 2000 and published in a peer-reviewed toxicology journal in 2003, which concluded that the listed ingredients including bentonite are "safe as used in cosmetic products". Cited only to fix the document history that the 2023 report reopened after fifteen years, and named separately from it because on this site a superseded conclusion and a current one are not interchangeable. It is a safety document, not a comedogenicity one.
  7. Foley NK. "Environmental Characteristics of Clays and Clay Mineral Deposits." US Geological Survey Information Handout, September 1999 A federal geological survey publication, cited only for material identity and provenance. It describes the formation of bentonite as "beds containing smectite-group clay minerals including montmorillonite", says such beds "usually form from altered volcanic ash, but other types of rock may also serve as sources", and notes that clays generally may be mixtures of clay minerals with clay-sized crystals of quartz, carbonate and metal oxides. It contains no cosmetic, dermatological or comedogenicity data of any kind and is not used here as evidence about skin.
  8. Salimi S, Fakhri M, Saeedi M, Rahimnia SM, Kazeminejad A, Moosazadeh M, Habibi E, Jokar A. "The Therapeutic Effects of a Bentonite-Based Facial Mask With Alcea sulphurea Extract on Acne Severity and Patient Experience: Add-On Randomized Controlled Clinical Trial." J Cosmet Dermatol 24(12):e70586 (2025). doi:10.1111/jocd.70586 The only randomised human trial of a bentonite-containing topical on acne that we found, read in full text (open access) rather than from its abstract. A TREATMENT study, not a comedogenicity test: 60 people with moderate acne in Sari, Iran, randomised to a bentonite and Alcea sulphurea mask or a placebo gel, both arms also taking oral azithromycin 250 mg, applied nightly for eight weeks and washed off after ten minutes; outcomes were total lesion count, an acne severity index and satisfaction, all assessed by a single investigator. Funded by Mazandaran University of Medical Sciences; the authors declare no conflicts. What it cannot support, from its own text: the mask combines bentonite with a plant extract at 1:1, so no arm isolates the clay; the two arms differed at baseline in age and education, and after the authors adjusted for both, the between-group p-values were 0.063 (lesion count) and 0.203 (severity index), neither of which the abstract reports; and the authors list the mask-versus-gel format difference as a threat to blinding. It counts lesions on treated acne, not comedones induced by an ingredient.
  9. Choi K, Liu H, Zhu Y, Jiang Z, Lu S. "A Case-Control Study Exploring the Association Between Cosmetic Use and Acne Risk: Implications for Prevention and Clinical Practice." Clin Cosmet Investig Dermatol 18:1833–1843 (2025). doi:10.2147/CCID.S533950 A single-centre case-control study of 151 participants — 81 with acne, 70 without — recruited at Sun Yat-sen Memorial Hospital, Guangzhou, between October 2022 and April 2023, using a self-administered questionnaire. Read from its abstract record. Its endpoint is self-reported product-category use against acne case status, not comedone counts and not ingredients. After adjustment for age, occupation, parental history and milk consumption, powder products remained an independent risk factor, odds ratio 3.47 (95% CI 1.58–7.59, p = 0.02). Cited because powders are a category bentonite appears in, and because a page that reported only the study pointing the reassuring way would be doing the thing this site exists to object to. It names no ingredient and, being observational, establishes association rather than cause.
  10. Marks JG Jr, Fowler JF Jr, Sherertz EF, Rietschel RL. "Prevention of poison ivy and poison oak allergic contact dermatitis by quaternium-18 bentonite." J Am Acad Dermatol 33(2):212–216 (1995) A human trial of a DIFFERENT MATERIAL, cited to keep it different. Quaternium-18 bentonite — bentoquatam, marketed as IvyBlock — is a quaternary-ammonium-modified clay, and this study tested it as a barrier lotion against urushiol in people allergic to poison ivy and oak, reporting absent or significantly reduced reactions at pretreated sites. Read from its abstract record. Its endpoint is allergic contact dermatitis, not comedones, and the material is a derivative rather than the parent clay. It supports nothing on this page except the point that the two must not be read across.
  11. acne.org — "What Is Comedogenicity, and What Ingredients Are Comedogenic? The Full Story" A secondary summary, and where many readers will have met a verdict on this mineral. Characterised precisely rather than dismissed: it walks through eleven comedogenicity studies with citations, states its own list rule — "avoid" means comedogenic in two or more rabbit assays or at least one human study — and says plainly that rabbit results do not necessarily transfer to humans. Inside its summary of the 1989 paper it prints "Mineral materials generally were non-comedogenic. They include clays, bentonite, kaolin, talc, iron oxide, chromium hydroxide, and titanium dioxide." That is a paraphrase rather than a row read off his table, and we have not traced it to any particular sentence in the paper. Whatever route it travelled, it is not a second measurement: the article attributes it to the same 1989 paper this page reads.

Others in the same family

Minerals & pigments behave similarly enough that the evidence for one is often wrongly read across to the others. These are its structural relatives, not a guess. What the evidence says about minerals & pigments as a family ›

Last reviewed 2026-08-20 · How we decide

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