Corn Oil

Corn oil is one of the ingredients where the legacy number is real and checkable, but not settled. Fulton's 1989 rabbit-ear assay scored it 3 of 5 — a grade he himself filed as "borderline" — while a second rabbit assay, run six years earlier at a different laboratory, scored it 0 to 1 — the bottom of the same 0-to-5 scale. That is not two labs agreeing, which is the useful case; it is two labs at opposite ends of the scale they share. Both are rabbits' ears, and we identified no human comedogenicity study of corn oil.

What it is

The triglyceride oil obtained from the germ of the maize kernel, Zea mays. It is a high-linoleic vegetable oil. The Codex Alimentarius standard for named vegetable oils, CXS 210-1999, gives maize oil's composition — measured by gas chromatography on authentic samples, and reported as ranges rather than a fixed recipe — as linoleic 34.0–65.6%, oleic 20.0–42.2%, palmitic 8.6–16.5%, stearic not detected to 3.3%, and myristic not detected to 0.3%. Linoleic acid — an 18-carbon fatty acid with two double bonds, written C18:2 — carries the highest of those ranges, though the linoleic and oleic ranges overlap between 34 and 42.2%, so the table does not establish that every batch is linoleic-dominated. The width of those ranges is worth holding on to: it is the practical form of the footnote Fulton attached to his whole oils section, that results depend on the source of the raw material. Outside cosmetics corn oil is best known as the neutral oil toxicology reaches for as a vehicle control — which is worth noting mainly so that a clean vehicle record is not mistaken for evidence about pores.

Why we rate it Caution

We rate it Caution. The evidence is two rabbit-ear assays, run at two laboratories, that do not agree. Fulton's 1989 table — the source nearly every comedogenic number online descends from — prints Corn oil at 3, in section VI, "Oils." We read the row off a render of the journal scan rather than off a list quoting it. It matters what a 3 meant to Fulton, because the lists that republish his numbers drop his key: "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." So corn oil's 3 is the top of the borderline band — not "not significant," and not "positive" either. One detail is worth stating precisely, because it is where the source-dependence caveat bites: several oils in this section carry a parenthetical second figure that Fulton defined as results using refined oil — avocado is 3(2), olive 2(1), almond 2(1). Corn oil is printed as a bare 3, with no refined-grade figure beside it, and it is not among the three oils — sesame, avocado and mink — that Fulton names in his body text as improving with refinement. He reported one number for it and no improved value, and the section still carries his heading footnote, "Results depend on source of raw material." Morris and Kwan, publishing in the Journal of the Society of Cosmetic Chemists in 1983 — six years before Fulton, at a different laboratory — ran their own rabbit-ear assay on 32 materials on the same 0-to-5 scale, and scored Corn Oil at 0 to 1 — the bottom of it. Fulton's own key would file a 0 to 1 as "not considered significant," but that key is Fulton's, and the Morris and Kwan paper as we hold it prints no interpretive bands of its own, so what we can say is that their number sits well below his on the scale the two share, not that they graded corn oil in his words. This is the part that makes corn oil different from the ingredients where two assays happen to agree. Here they disagree, and by a wide margin. Morris and Kwan were not deferential to Fulton — the same paper openly contradicts him on sodium lauryl sulfate and says so in print — so the 0 to 1 is an independent measurement, not a copy of his, and the gap between it and his 3 is a real gap, not a rounding difference. A shared 0-to-5 scale is not a shared protocol, though, and the two are not directly comparable readings: Fulton applied the oil at roughly 10% in propylene glycol, Morris and Kwan applied it undiluted, and neither paper says whose corn oil it was or how it was processed. Caution reflects the higher of the two readings. A reader who gave more weight to the independent, undiluted Morris and Kwan result could reasonably read this oil as Clear, and we would not be able to say they were wrong.

What the evidence doesn’t tell you

We identified no human comedogenicity study of corn oil — not on a face, not on a back, not with a comedone count. Everything above happened inside the ear of a rabbit: Fulton at roughly 10% in propylene glycol, Morris and Kwan undiluted in the ear canal, both scoring follicular keratosis by microscope. Fulton called his own 220-row survey "not at all definitive but simply designed to stimulate research," and warned the rabbit ear is sensitive enough that "not everything that irritates this model will also irritate human skin." His oils section carries the footnote "Results depend on source of raw material," attached to the heading and so applying to corn oil as much as to the butters. A number from one batch of corn oil in one decade is not a promise about the bottle in hand. The disagreement is itself a limit, and it cuts the other way from a rating built on agreement. Where castor oil has two labs landing on the same low number — 1 from Fulton, 0 to 1 from Morris and Kwan — corn oil has one lab at borderline and one at not-significant. Two rabbit assays that contradict each other are weaker evidence than two that concur, and a Caution resting on the higher of them is a defensible reading of unsettled data, not a measured fact about the oil. What neither paper records is the supplier, grade or processing of the oil it tested, so we cannot say whether the two laboratories put the same material on a rabbit. Source and grade are plausible contributors to the disagreement. The papers do not establish that they caused it, and other differences between the protocols would do just as well. The composition invites a tidy story, and we are going to leave it uninvited. Corn oil is high in linoleic acid and comparatively low in oleic — the opposite of the fatty-acid profile usually blamed for pore-plugging — and the content farms run the argument in reverse, asserting that its omega-6 content "triggers inflammation and breakouts." Neither version is backed by a comedogenicity measurement of corn oil. The linoleic-versus-oleic sebum literature is real, but it has not been tested on this oil, and a mechanism that would explain a result is not additional evidence for it. We are not going to write it as though somebody had run that study. Two things that are not comedogenicity data, flagged so they are not mistaken for it. The Cosmetic Ingredient Review's 2011 assessment concludes corn-derived ingredients are safe as used in cosmetics, and records that studies of many other endpoints "use corn oil as a vehicle control with no reported adverse effects at levels used in cosmetics" — but safety and a clean vehicle record are different questions from follicular plugging, and the abstract we read says nothing about comedogenicity at all. And the field-wide caveat, from a 2025 review in JAAD Reviews surveying the literature from 1972 on: no standardised comedogenicity test exists, and "non-comedogenic" is an unregulated label.

Where you’ll see it

Corn oil is a cosmetic ingredient — the Cosmetic Ingredient Review assessed it as one in 2011 — and it is also a kitchen oil that people apply to skin straight from the bottle. We are not going to be more specific than that. We could not open a document that would let us state its current cosmetic functions, its prevalence, or a maximum use concentration, and an earlier version of this page attributed such figures to a source that does not contain them. On a label it usually appears as Zea Mays (Corn) Oil; a corn-germ-oil declaration is also in use. Whether those two names always denote the same commercial material is not something we verified against a nomenclature authority, and neither historical assay says which declaration, grade or refining state its sample would carry today.

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 of our legacy score and of nearly every comedogenic number in circulation. Method: the ingredient at roughly 10% in propylene glycol, applied to the inner ear of New Zealand albino rabbits, three rabbits per assay, follicles scored for keratosis on a 0–5 scale. Read off a render of the journal scan, not off a list quoting it. Its Table I, section VI "Oils," prints Corn oil at 3 — a bare 3, with no parenthetical "refined oil" figure of the kind it prints for avocado 3(2), olive 2(1) and almond 2(1). It also supplies the grade key the lists omit — 0 to 1 "is not considered significant," 2 to 3 is "borderline," 4 to 5 is "considered positive" — and the section footnote on every oil and butter: "Results depend on source of raw material." It records no supplier or grade for the corn oil tested. Fulton called the survey "not at all definitive."
2. 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) A second, independent rabbit-ear assay from a different laboratory, six years earlier, on the same 0–5 scale — and the reason this page can say two measurements exist and disagree, rather than "one study, quoted often." Thirty-two materials: three rabbits, ear canal, undiluted unless stated, 14 applications, microscopic grading only. Its oils table is printed rotated and returns nothing to OCR, so the score here is taken from our own verbatim transcription. It scores Corn Oil at 0 to 1 — the bottom of the shared 0–5 scale, and well below his 3 — and, like Fulton, records no supplier or grade. What we hold of it prints no interpretive band key of its own, so we do not lend it Fulton's grade language. It is not a deferential republication of him: the same paper flatly contradicts him on sodium lauryl sulfate and prints the disagreement, which is what makes its lower corn-oil figure an independent reading rather than a copy. The shared scale is not a shared protocol. Still a rabbit's ear, still not a person.
3. Codex Alimentarius Commission. "Standard for named vegetable oils." CXS 210-1999, Table 1 (adopted 1999; revised 2001, 2003, 2009) An international food standard, read in full as a public PDF. Cited for one thing only: its Table 1, "Fatty acid composition of vegetable oils as determined by gas liquid chromatography from authentic samples," which gives maize oil as linoleic 34.0–65.6%, oleic 20.0–42.2%, palmitic 8.6–16.5%, stearic ND–3.3% and myristic ND–0.3% of total fatty acids. It describes composition, not skin behaviour: it counts no comedones, tests nothing on any animal or person, and has no bearing on the rating. It is here because this page previously carried fatty-acid percentages attributed to a source that does not print them.
4. Andersen FA, Bergfeld WF, Belsito DV, et al. (Cosmetic Ingredient Review Expert Panel). "Final report of the safety assessment of cosmetic ingredients derived from Zea mays (corn)." Int J Toxicol 30(3 Suppl):17S–39S (2011) An independent expert-panel safety review, not a comedogenic list and not downstream of Fulton. We have read only the published abstract; the full report is paywalled. The abstract supports three things and we cite it for those three: that the Panel concluded corn-derived ingredients are safe in the practices of use and concentration it assessed, that studies of many other endpoints "use corn oil as a vehicle control with no reported adverse effects at levels used in cosmetics," and that safety data were extrapolated across the group because test data were unavailable for most of the ingredients. It does not print fatty-acid percentages, cosmetic functions or a maximum use level, and an earlier version of this page said it did. It assesses safety, not comedogenicity, and the abstract says nothing about pores — which is itself worth knowing. We could not open the full report, so we have not read its bibliography; our statement that we found no human comedogenicity study of corn oil is bounded by the documents we could open.
5. "Comedogenicity in cosmeceuticals: a review of clinical relevance, regulatory gaps, and future directions." JAAD Reviews (2025) Recent peer-reviewed review of the whole field, covering the literature from 1972 onward. It is a synthesis of the legacy literature, not a new measurement, and independent of Fulton only in authorship, since the corpus it surveys includes his. Finds that no standardised comedogenicity test exists and that "non-comedogenic" is an unregulated label. Cited for the field-wide caveat, not for anything specific to corn oil. The journal is new enough that we could not retrieve a volume and page range or a full author list for it.
6. acne.org comedogenic ingredient list, and the comedogenic-rating charts generally The source recorded against corn oil in our own ratings file, and the kind of page a reader is likeliest to have met a comedogenic number on. It is a consumer chart, not a measurement. We are not going to claim more about it than we checked: acne.org describes its list as drawing on 11 studies using the rabbit-ear or human method, not on Fulton alone, and we did not confirm that it carries a corn oil row at all. Where the 3 that circulates for corn oil was copied from, and by whom, we did not trace. What we can say is that a chart printing a bare 3 carries neither Fulton's grade key nor Morris and Kwan's 0 to 1, so the number arrives looking more settled than the evidence behind it is.

Others in the same family

Oils 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 oils as a family ›

• Argan Oil Clear Low
• Avocado Oil Caution Low
• Castor Oil Clear Moderate
• Coconut Oil Clogging Moderate
• Cottonseed Oil Caution Low
• Evening Primrose Oil Caution Low
• Flaxseed Oil Caution Low
• Grapeseed Oil Caution Low

Last reviewed 2026-08-01 · How we decide

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