Soybean Oil
Soybean oil is rated Caution, and the number behind it is real but thin. Fulton's 1989 rabbit-ear assay scored it 3 of 5 — a grade he himself filed as "borderline," not positive — and that single reading is the whole of the measured evidence. None of the three other rabbit-ear papers we hold carries a soybean oil row, and we found no test of this oil on a human face. Caution reflects one borderline result with nothing to confirm or contradict it.
Vegetable oil with a moderate legacy clog score.
What it is
The oil pressed and refined from the seeds of the soybean, Glycine max, labelled on cosmetics as Glycine Soja Oil. It is a high-linoleic vegetable oil, and one of the few common cosmetic oils to carry a meaningful fraction of alpha-linolenic acid, the omega-3. The Cosmetic Ingredient Review's 2017 assessment of plant-derived fatty acid oils describes soybean oil as triglycerides of oleic, linoleic, linolenic and saturated acids; published analyses put linoleic acid at roughly half of it, oleic acid and the saturated acids palmitic and stearic making up much of the remainder, and alpha-linolenic a smaller but real share — figures that move with cultivar and refining, which is why we give them as approximate. It also carries tocopherols (vitamin E) natively. We flag the composition to describe the material, not to argue about pores. In a formula it works as an emollient and skin-conditioning oil, and it has a long parallel life as a food and frying oil. On a label it appears as Glycine Soja (Soybean) Oil.
Why we rate it Caution
We rate it Caution, and the rating rests on a single legacy rabbit-ear score with nothing beside it. Fulton's 1989 table — the source nearly every comedogenic number online descends from — prints Soybean 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. What a 3 meant to Fulton is the part the charts drop: his own key 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." So soybean oil's 3 sits at the top of the borderline band — above "not significant," but short of the "positive" grades. It is printed as a bare 3, with none of the parenthetical second figure Fulton used for oils whose refined grade tested lower — sesame 3(1), avocado 3(2), olive 2(1) — so he recorded one number for it and no improved value. The section carries his heading footnote, "Results depend on source of raw material," and Fulton named neither supplier nor grade for what he tested. One detail from the same table is worth stating precisely, because it is a caution against reading any soybean-derived number as "soybean oil's number." Fourteen rows below the oil, Fulton prints "Maleated soybean oil" at 0 — a chemically derivatised material, not a grade of the oil, scored clean. It tells you nothing about the plain oil, and we are not using it as evidence about the plain oil; it is here only to show that Fulton's table distinguishes the base oil from its derivatives, and that the score travels with the exact material, not with the word "soybean." The point that separates soybean oil from the oils where two labs agree, or disagree, is that we found no second reading of it anywhere in the primary assays we hold. Morris and Kwan, in the Journal of the Society of Cosmetic Chemists in 1983, ran an independent rabbit-ear assay on the same 0-to-5 scale, and it is genuinely independent of Fulton — the same paper contradicts him in print on sodium lauryl sulfate. But their vegetable-oil set was nine oils — olive, avocado, castor, corn, sesame, safflower, peach kernel, grape seed and sweet almond — and soybean was not one of them. Fulton's own earlier paper, the 1984 rabbit-ear table we hold in full, carries no soybean oil row either. And the only later rabbit-ear survey we can find, Nguyen, Dang and Maibach in 2007, tested esters and a handful of other materials — isopropyl palmitate and myristate, butyl stearate, decyl oleate, cetyl and stearyl alcohol, petrolatum and the rest — and no vegetable oils at all. So Fulton's 3 is neither confirmed by a second reading nor pulled down by one; it stands alone. Caution reflects that one borderline result, taken at face value.
What the evidence doesn’t tell you
We identified no human comedogenicity study of soybean oil — no count of comedones on a face, or a back, after using it. The human trials of soybean oil we did find are dietary, about circulating lipids, or neonatal skin-barrier studies, and none of those counted comedones. Everything the rating leans on happened inside the ear of a rabbit, once: Fulton's assay at roughly 10% in propylene glycol, follicular keratosis scored by microscope. Fulton called his own 220-row survey "not at all definitive but simply designed to stimulate research," and warned that the rabbit ear is sensitive enough that "not everything that irritates this model will also irritate human skin." The source-dependence caveat has real force here. Fulton's oils footnote — "Results depend on source of raw material" — is attached to the section heading, so it governs soybean oil as much as the butters, and soybean oil's own published composition swings with cultivar and refining. A single grade from one batch of soybean oil in the 1980s is a weak promise about the bottle in hand, and with only that one grade on record there is no range to reason across. The maleated-soybean-oil row does not fill that gap and we are not going to use it to: maleated soybean oil is a chemically derivatised material rather than a differently refined grade of the oil, so its 0 says nothing about how much the plain oil moves with its source. The composition invites a tidy story, and we are going to leave it uninvited. Soybean oil is linoleic-rich and carries a fraction of omega-3 alpha-linolenic acid — close to the opposite of the oleic-heavy profile usually blamed for pore-plugging — and the content farms run the argument both ways, some calling it "non-comedogenic" on that basis and others asserting its omega-6 content "triggers inflammation and breakouts." Neither version is backed by a comedogenicity measurement of soybean oil. A mechanism that would explain a result is not additional evidence for it, and we are not going to write one as though somebody had run the study. Two things that are not comedogenicity data, flagged so they are not mistaken for it. The CIR's 2017 assessment concludes the plant-derived fatty acid oils, soybean oil among them, are safe as used in cosmetics — but safety is a different question from follicular plugging, and the report says nothing about comedogenicity. 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
On a label it appears as Glycine Soja (Soybean) Oil. The Cosmetic Ingredient Review lists the plant-derived fatty acid oils, soybean included, as skin-conditioning, emollient and occlusive agents, so it turns up as a general-purpose emollient — in creams, lotions, cleansers, soaps and some colour cosmetics — and it has a long parallel life as a food and frying oil and as a carrier oil. Several distinct INCI materials share the word: Hydrogenated Soybean Oil, Soybean Glycerides and the maleated oil Fulton scored at 0 are different entries with their own identities, and only Glycine Soja (Soybean) Oil is the material carrying the 3. Fulton named neither supplier nor grade for the oil he tested, and we hold no figures on which grades reach cosmetic formulas; his caveat is that the source and refining of the raw material can move the result, not that these are separate ingredients.
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.
- 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 Soybean oil at 3 — a bare 3, with no parenthetical "refined oil" figure of the kind it gives for sesame 3(1), avocado 3(2) and olive 2(1) — and, separately, "Maleated soybean oil" at 0, a different, chemically modified material. It 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." Fulton named no supplier or grade for the oil he tested, and called the survey "not at all definitive."
- 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 rabbit-ear assay from a different laboratory, six years earlier, on the same 0–5 scale — three rabbits, ear canal, undiluted unless stated, 14 applications, microscopic grading — and it is genuinely independent of Fulton, contradicting him in print on sodium lauryl sulfate. Cited here for what it does NOT contain: its vegetable-oil set is nine oils (olive, avocado, castor, corn, sesame, safflower, peach kernel, grape seed, sweet almond), and soybean is not among them. So this paper adds no second reading of the oil to confirm or contradict Fulton's 3 — part of the reason this page can say the score stands alone.
- Fulton JE, 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) Fulton's own earlier rabbit-ear paper, on its own 0–5 scale, whose key reads 1–2 not significant and 3 or above considered positive. Cited here for what it does NOT contain: no soybean oil row. We hold its table in full, so the absence is verified rather than assumed. It means the 1989 3 is not a second reading of an earlier one, and Fulton himself put this oil on the bench once.
- Nguyen SH, Dang TP, Maibach HI. "Comedogenicity in rabbit: some cosmetic ingredients/vehicles." Cutan Ocul Toxicol 26(4):287–292 (2007) The only later rabbit-ear comedogenicity survey we could find, on a 0–4 scale — cited, like Morris and Kwan, for what it does not contain. Its test set is esters and a handful of other materials (isopropyl palmitate, isopropyl myristate, butyl stearate, isopropyl isostearate, decyl oleate, isostearyl neopentanoate, isocetyl stearate, myristyl myristate, cocoa butter, cetyl alcohol, paraffin, stearyl alcohol, sodium lauryl sulfate, petrolatum); no vegetable oils, and no soybean. It is the basis for the bounded statement that no rabbit-ear survey we could trace after Fulton put soybean oil on the bench, not evidence about the oil.
- Burnett CL, Fiume MM, Bergfeld WF, Belsito DV, Hill RA, Klaassen CD, Liebler D, Marks JG Jr, Shank RC, Slaga TJ, Snyder PW, Andersen FA. "Safety Assessment of Plant-Derived Fatty Acid Oils." Int J Toxicol 36(3 Suppl):51S–129S (2017) An independent Cosmetic Ingredient Review Expert Panel safety review covering 244 plant-derived fatty acid oils, Glycine Soja (soybean) oil among them — not a comedogenic list and not downstream of Fulton. Cited for what it can support: the material's fatty-acid character (triglycerides of oleic, linoleic, linolenic and saturated acids; linoleic-rich), its cosmetic functions (skin-conditioning, emollient, occlusive), and the Panel's conclusion that these oils are safe as used. It assesses safety, not comedogenicity, and says nothing about pores. Composition figures on this page are given as approximate because published analyses of soybean oil vary with cultivar and refining.
- "Comedogenicity in cosmeceuticals: a review of clinical relevance, regulatory gaps, and future directions." JAAD Reviews (2025) A 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 soybean oil.
- acne.org comedogenic ingredient list, and the comedogenic-rating charts generally Where a reader will most likely have met soybean oil's "3." These charts republish the Fulton 1989 rabbit-ear scores; they are not independent measurements, and neither are CosDNA, Face Reality or Banish. On soybean oil they pass along Fulton's 3 without his grade key — so a number he called borderline arrives read as "clogging" — and without the fact that we found no second reading of it in the other primary assays. Cited as the genealogy of the circulating figure, not as corroboration.
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 ›
Last reviewed 2026-08-12 · How we decide