Porecelain

Flawless skin starts with the fine print.

Iron Oxides

Iron Oxides is rated Clear, and for once the circulating number matches the name it is quoted under: Fulton's 1989 rabbit-ear table has an "Iron oxides" row and it reads 0, and his 1984 paper prints 0–1 for the same name under a different key. The two agree, but both are his: the 1989 row was read at roughly 10% in propylene glycol, the 1984 paper does not record what its row was carried in, and "Iron Oxides" is a plural name covering three separate compounds that neither paper distinguishes. The only recent human data that touches the products iron oxides live in — powders and foundations — is a product-category association, and cannot say which ingredient is responsible.

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

Fulton 1989 scored 0 and Fulton 1984 0-1 of 5 — two readings, one programme.

What it is

A group of inorganic pigments: the colour in almost everything that has to match skin. On a label they appear as Iron Oxides, or as the colour index numbers CI 77491 (red), CI 77492 (yellow) and CI 77499 (black). A single shade is usually a blend of all three, which is why the INCI name is plural. Cosmetic iron oxides are not mined ochre. The FDA's colour-additive listing defines the additive as "any one or any combination of synthetically prepared iron oxides, including the hydrated forms", "free from admixture with other substances", sets limits for arsenic, lead and mercury, and permits it in cosmetics generally, including in the eye area, in amounts consistent with good manufacturing practice. It is exempt from batch certification. That quoted wording is part of the identity standard the listed additive has to meet; it is not a statement about the supplier dispersions, treated grades or finished blends the pigment reaches a formula in. And, as with titanium dioxide, the pigment is not always supplied bare. Surface-treated grades exist — treated so they wet, disperse and stay put — and the treatment is itself co-listed on the label. We hold no figure for how much of the market is treated. A silane supplier's published formulary lists them as "Iron Oxides (&) Stearyl Triethoxysilane", "(&) Dimethicone", "(&) Triethoxycaprylylsilane", "(&) Polydiethylsiloxane", "(&) Trimethylsiloxysilicate" and "(&) Disodium Carboxyethyl Siliconate". Fulton records no treatment, no shade, no grade and no supplier for what he tested, so the treatment status of the samples behind both of his readings is unknown to us.

Why we rate it Clear

We rate it Clear at Low confidence. Fulton's 1989 rabbit-ear survey has a row printed under the name that appears on the label. The row is printed "Iron oxides" and reads 0 on his 0–5 scale, and by his own published key a grade of 0 to 1 "is not considered significant." The method behind the number is the one most circulating comedogenic scores rest on: the test material at roughly 10% in propylene glycol, applied to the inner ear of New Zealand albino rabbits, three rabbits per assay, five days a week for two weeks, follicular keratosis measured under a micrometer. Saying that the row exists is worth more here than it sounds, because it is not the usual finding on this site. A great many of the numbers we check turn out to belong to a different molecule, a different grade of the same plant, or to no document at all. This one is printed against the name it is quoted under. There is a second reading, five years earlier, and it carries its own key. Fulton's 1984 paper with Pay and Fulton prints "Iron oxides — 0–1" in Table I under "Miscellaneous pigments", beside four rows at the same 0–1, printed in that paper's own spelling as "Ultramarine Violet", "Carmine", "Chrominum hydroxide" and "Titanium dioxide". Each of those four carries an asterisk and the iron oxides row does not, which tells us the four were diluted and leaves the iron oxides carrier unstated rather than telling us anything about its source. That paper's thresholds are not the 1989 ones: there, "a minimal grade of 1 to 2 is not considered significant", and 3 or above is considered positive. So 1984 reads not significant, 1989 reads 0, and the two agree. They are two readings from one investigator's programme, made under conditions we cannot match to each other, not replication by a second laboratory. The row sits in a block worth describing. In the 1989 table the entries immediately around it are a run of D&C reds scoring between 1 and 3, followed by a short group of inorganic colourants — "Ultamarine violet", "Iron oxides", "Carmine", "Titanium dioxide" — every one of which prints 0. The 1984 pigment block reads the same way, with the organic dyes at 2 to 4 and the mineral ones at 0–1. That is a description of how two tables are laid out. It is not a further experiment on iron oxides, and it does not raise our confidence in the 0. Confidence stays Low because of what those two readings are. Legacy rabbit-ear grades from a single investigator, on samples he does not describe, are legacy-assay evidence and nothing more. "Inert mineral" is a description of a material, not a measurement of what it does in a follicle, and we have no mechanism we can cite that anyone has tested in one.

What the evidence doesn’t tell you

Neither reading was carried through a range of vehicles, and Fulton's own Table II is the reason that matters. He took a single pigment, D&C Red #36, through four carriers and printed four different grades: 3 in mineral oil, 2 in pentaerythrital tetra capra/caprylate, 1 in propylene glycol, and 0 in PEG 400. That is one pigment moving three grades on the carrier alone. It is a different pigment from this one — a synthetic organic dye, not an inorganic oxide — so it is not a result about iron oxides in any direction. What it does show is that a pigment's grade in this model is a property of the pigment and its vehicle together, and the iron oxides rows were not put through that exercise: the 1989 row was read at roughly 10% in propylene glycol, and the 1984 paper does not record what its row was carried in. "Iron Oxides" is also a plural, and neither paper says which. The INCI name covers red, yellow and black oxides, hydrated and anhydrous, supplied singly or blended; Fulton's tables print the plural and stop there. A grade recorded against an unspecified mixture cannot be assigned to any one of its members, and it cannot be assumed to hold for a surface-treated grade, which is a different physical material with a second ingredient bonded to it. One small thing we cannot resolve from the page. In the 1984 table, four of the five entries in the "Miscellaneous pigments" block carry an asterisk and "Iron oxides" does not. That paper's footnote defines the asterisk: those materials "were either diluted with mineral oil or incorporated into an alcohol gel at a 10% concentration", while everything unmarked "was used 'as is' if the agent was a liquid or soft solid". A dry pigment is neither, so the unmarked row and the footnote do not sit together. We report the number as printed and flag that we do not know how the 1984 sample was carried. The general cautions apply to a 0 exactly as they apply to a 4. These are rabbit-ear readings; the rabbit ear is not a face; Fulton called his own survey "not at all definitive but simply designed to stimulate research"; and Draelos and DiNardo's 2006 re-evaluation found finished products testing non-comedogenic on human backs despite containing ingredients the rabbit assay had flagged. A 2025 review in JAAD Reviews, surveying the field from 1972 onward, found that no standardised comedogenicity test exists and that "non-comedogenic" is an unregulated claim. We identified no human comedogenicity study of iron oxides, and no comedogenicity measurement of them from a laboratory other than Fulton's in the sources we searched. Morris and Kwan's 1983 rabbit-ear paper does not test them, and the materials named in Nguyen and Maibach's 2007 assay do not include them. Where consumer ingredient references state that mineral materials were non-comedogenic and name iron oxide among them, they are summarising Fulton 1989: acne.org's article says so in the body of its account of that paper and footnotes it to that reference. That is a republication with its source disclosed, not a second finding. What complicates the page is not another assay but a human study of the wrong grain size. Choi and colleagues' 2025 case-control study of 151 participants in Guangzhou asked people what they used and compared cases with controls. Facial cleansers, foundation and powders were each associated with increased odds of acne, and after adjustment for age, occupation, parental history and milk consumption, powders remained an independent risk factor, with an odds ratio of 3.47 (95% CI 1.58–7.59). Powders and foundations are where iron oxides live. But that study measured self-reported product-category use, not ingredients: it names no ingredient, it cannot separate the pigment from the binder, the filler or the act of wearing makeup at all, and a questionnaire-based case-control design shows association, not cause. It does not contradict the 0. It is a reminder that the 0 is a number about a pigment, not about a compact. Finally, the regulatory position is not evidence about pores. The FDA lists iron oxides as safe for colouring cosmetics generally, and the EU permits them without restriction subject to purity. Those are safety determinations. Safety and comedogenicity are different questions, and a colour-additive listing says nothing about a follicle in either direction.

Where you’ll see it

On labels as Iron Oxides, or as CI 77491, CI 77492 and CI 77499 — the strings people paste into a checker straight off a foundation carton. They carry the colour in foundation, concealer, tinted moisturiser, BB and CC cream, loose and pressed powder, bronzer, blush, eyeshadow, eyeliner, mascara, brow products and lipstick, and in tinted mineral sunscreens. The amount used tracks the depth of the shade rather than the product category, so label position tells a reader very little. For concrete figures we have only worked examples: a silane supplier's published formulary gives a satin-feel liquid foundation carrying 1.9% iron oxides across three shades, a powder-cream concealer at 3.5%, and a waterproof mascara at 12% black iron oxide. Those are that supplier's demonstration formulas, not a survey of the market. In each of them the pigment is a surface-treated grade, and the treatment is listed on the label beside it.

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 one of the two documents in the corpus we searched that put a number against this material. A rabbit-ear survey: test material at roughly 10% in propylene glycol, applied to the inner ear of New Zealand albino rabbits, three rabbits per assay, five days a week for two weeks, follicular keratosis measured with a micrometer. Read here off our own 400dpi transcription of Table I rather than a chart quoting it. "Iron oxides" has its own row, scored 0, in the pigment section — the neighbouring D&C reds run 1 to 3 and the other inorganic colourants (printed "Ultamarine violet", "Carmine" and "Titanium dioxide") print 0. Fulton's grade key: 0–1 "is not considered significant". Table II of the same paper grades D&C Red #36 at 3, 2, 1 and 0 in four different vehicles. The paper records no shade, grade, surface treatment or supplier for the iron oxides sample, and Fulton describes the whole survey as "not at all definitive but simply designed to stimulate research".
  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 earlier rabbit-ear survey from the same investigator, read off a 400dpi render of the journal scan. Method: two New Zealand albino rabbits per test, material applied to the inner surface of one ear daily for two weeks with the other ear as control, follicular hyperkeratosis graded 0–5 and borderline cases confirmed by microscopic biopsy. Table I prints "Iron oxides — 0–1" under "Miscellaneous pigments". Two things belong to this paper and not to the 1989 one. Its key: "a minimal grade of 1 to 2 is not considered significant", with 3 or above considered positive — so the same digit does not mean the same thing across Fulton's two papers. And its asterisk, which marks materials diluted in mineral oil or gelled in alcohol at 10%, unmarked materials being used "as is" if liquid or soft solid; the iron oxides row is unmarked and we cannot tell from the page how a dry pigment was carried. A second reading by the same group, concordant with 1989, and not independent replication.
  3. 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 at Sun Yat-sen Memorial Hospital, Guangzhou, using a self-administered questionnaire about cosmetic use. Authors declare no conflicts. Its endpoint is self-reported product-category exposure against acne case status, not comedone counts and not ingredients: facial cleansers (P=0.04), foundation (P=0.03) and powders (P=0.01) were associated with increased acne risk, and after adjustment for age, occupation, parental history and milk consumption, powders remained an independent risk factor, OR 3.47 (95% CI 1.58–7.59). Cited here because powders and foundations are the categories iron oxides live in. It names no ingredient, cannot attribute the association to any component of a product, and being observational and questionnaire-based, it establishes association rather than cause. It is not a comedogenicity assay of iron oxides and cannot be read as one.
  4. Draelos ZD, DiNardo JC. "A re-evaluation of the comedogenicity concept." J Am Acad Dermatol 54:507–512 (2006) A Current Issues and Opinion piece that tested finished products on human upper backs and found products testing non-comedogenic despite containing ingredients the rabbit assay had flagged. Cited only for the caveat it establishes — that an ingredient's grade does not transfer cleanly to the formula it ends up in, in either direction. It is not a study of iron oxides, and it is not a same-substance validation of the rabbit assay against human skin.
  5. "Comedogenicity in cosmeceuticals: a review of clinical relevance, regulatory gaps, and future directions." JAAD Reviews (2025) A peer-reviewed review of the field covering literature from 1972 to 2025, finding that no standardised comedogenicity test exists and that "non-comedogenic" is an unregulated label. A synthesis of the legacy corpus rather than a new measurement, and independent of Fulton only in authorship, since the literature it surveys includes his. Cited for the field-wide caveat.
  6. US Food and Drug Administration. 21 CFR 73.2250, "Iron oxides" (Listing of Color Additives Exempt from Certification, Subpart C — Cosmetics). eCFR text current as of 6 August 2026 The federal colour-additive regulation, cited only for material identity and regulatory status — it contains no comedogenicity data and makes no claim about pores. It defines the additive as "any one or any combination of synthetically prepared iron oxides, including the hydrated forms", "free from admixture with other substances" — the identity standard the listed additive has to meet, not a description of the dispersions, treated grades or finished blends a formulator buys — sets limits of 3 ppm arsenic, 10 ppm lead and 3 ppm mercury, permits use in cosmetics generally including the eye area in amounts consistent with good manufacturing practice, and exempts batches from certification. A safety and purity instrument, not evidence of noncomedogenicity.
  7. Gelest, Inc. "Tailoring Surfaces for Cosmetic Innovation" (2019), supplier formulary and surface-treatment brochure A promotional technical brochure from a silane and silicone manufacturer that sells the pigment surface treatments it describes, so its commercial interest is direct and its formulas are demonstrations rather than market data. Not a comedogenicity source. Cited for two concrete things it documents: that cosmetic iron oxides are routinely supplied surface-treated, with the treatment co-listed in the INCI name ("Iron Oxides (&) Stearyl Triethoxysilane", "(&) Dimethicone", "(&) Triethoxycaprylylsilane", "(&) Polydiethylsiloxane", "(&) Trimethylsiloxysilicate", "(&) Disodium Carboxyethyl Siliconate"); and worked use levels in its own published formulas — 1.9% total iron oxides in a satin-feel liquid foundation, 3.5% in a powder-cream concealer, 12% black iron oxide in a waterproof mascara.
  8. Kern D. "What Is Comedogenicity, and What Ingredients Are Comedogenic? The Full Story." Acne.org, last updated 24 March 2022 A consumer article by a commercial acne-products site, not a study. Included because it is the most-read source of the claim that iron oxide is non-comedogenic, and because it discloses where that claim comes from: the sentence appears inside its summary of "Study #9", which it footnotes to Fulton 1989. So on this ingredient it is a republication with its source named, not an independent corroboration. Its own methods section is a fair account of the rabbit-ear and cyanoacrylate-biopsy models and is not disputed here.

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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