Flaxseed Oil

Flaxseed oil is rated Caution, and its comedogenic 3 is not the mild number it looks like: secondary tabulations put it at the top of Kligman's 0-to-3 rabbit-ear scale — a ceiling, not a middle — though we have not read the primary tables, and Fulton, the paper usually credited with the comedogenic scale, never tested the oil at all.

What it is

Flaxseed oil and linseed oil are the same material: the oil pressed from the seed of Linum usitatissimum. The culinary and supplement trade calls it flaxseed; the industrial world and the older scientific literature call it linseed, and linseed is the name under which it was actually put on a rabbit's ear and given a comedogenic number. On a label it usually reads Linum Usitatissimum (Linseed) Seed Oil. It is a "drying oil" — unusually high in alpha-linolenic acid, a polyunsaturated omega-3 fatty acid — which is why the same botanical oil that sits in a facial serum is also the traditional binder in oil paint and wood varnish: it polymerises on exposure to air. Formulators reach for it as an emollient and as an omega-3 talking point. Hold on to the two names, because the split between them is not cosmetic. It is the reason the same oil is described in one place as never tested and in another as among the most comedogenic materials in the studies that did test it.

Why we rate it Caution

We rate it Caution at Low confidence, on a legacy rabbit-ear assay — and the number behind it has been misread in a specific, correctable way. Start with the scale, because it is the whole point. The comedogenic score that follows flaxseed oil around is 3. On the 0-to-5 scale most people picture — Fulton's — a 3 reads as middling, a score in the middle of the range. But this 3 was never on a 0-to-5 scale. It comes from Albert Kligman's rabbit-ear work, which runs 0 to 3. On that scale a 3 is not the middle. It is the top. The same digit means "borderline" in one paper and "the most comedogenic thing we tested" in another, and flaxseed oil's belongs to the second kind. Where it comes from. Two studies, both Kligman's, both rabbit-ear, both 0 to 3. Kligman and Mills, "Acne cosmetica," Archives of Dermatology, 1972 — the paper that coined the term and built the assay. And Kligman and Kwong, "An improved rabbit ear model for assessing comedogenic substances," British Journal of Dermatology, 1979. In the 1972 study, linseed oil is named among the most comedogenic of the vegetable oils tested, alongside cocoa butter and olive oil. In the 1979 study of sixteen materials, linseed oil again appears among the most comedogenic, alongside cocoa butter, squalene, pine tar and oleic acid. What we actually read, stated plainly, because on this page it matters. We read the 1979 abstract in full: sixteen materials, a 0-to-3 scale, whole-mount and histological scoring, "agreement excellent." The abstract names no individual ingredient. We were not able to open the printed data tables of either the 1972 or the 1979 paper. So the identification of linseed oil as one of the most comedogenic materials in each — and the specific figure of 3 — we take from a secondary tabulation of the two studies, not from having read the rows ourselves. The direction is well attested and it is consistent across both papers; the exact printed cell we report at second hand, and we flag it as such rather than dress it up as a reading of the primary table. The paper it is usually blamed on did not test it. Search this ingredient and the number will be presented as though it came from Fulton's 1989 survey, the source of nearly every comedogenic score in circulation. It did not. We rendered Fulton's 220-row table at 400dpi and read it by eye: its oils section runs cocoa butter, coconut butter, hydrogenated vegetable oil, sesame, corn, avocado and the rest, and it contains no linseed row and no flaxseed row anywhere in the paper. The common citation is wrong twice over — wrong scale, and wrong paper. One thing that is unusual here, and worth saying because it is the reverse of most pages on this site. The flaxseed number does not descend from Fulton. Fulton never tested the oil; the score predates his 1989 survey and rests entirely on Kligman. What it does not have is agreement across independent laboratories: the 1972 and 1979 results share a lead investigator and a method, seven years apart, so they are a replication by one group rather than two labs arriving at the same answer. We identified no linseed or flaxseed row in the one other 0-to-5 assay whose table we hold, Morris and Kwan 1983.

What the evidence doesn’t tell you

The instrument under this rating is the weakest kind the field has: test material applied to the inner ear of albino rabbits, follicular keratosis scored under a microscope. (We did not verify the exact concentration or vehicle Kligman used for this row, and do not import Fulton's.) It is not a human face, not a finished formula, and not a realistic concentration. And the man who built the assay later turned on it. Kligman's 1996 paper — "Petrolatum is not comedogenic in rabbits or humans: a critical reappraisal of the rabbit ear assay and the concept of acne cosmetica" — argued that the model over-calls bland occlusive greases. He issued no retraction of the 1972 work; his target was petrolatum and inert greases, not a drying oil like this one. So it neither clears flaxseed nor convicts it. It is a general reason to hold the whole legacy tier at Low confidence, and we do. What the assay measured was rabbit follicular keratosis, not comedones counted on a person. We identified no human comedogenicity study of flaxseed or linseed oil. A high rabbit-ear score was often treated as a reason to go on and test a material on human skin rather than as a verdict in itself; as far as we found, for this oil, nobody did. There is a counter-claim in circulation, and it is worth handling directly because it is false for a nameable reason. Some sources state flatly that flaxseed oil has never been assessed for comedogenicity. It has — twice — but under the name linseed, and those sources did not connect the culinary name to the industrial one. The wider disagreement in the popular lists, which variously give flaxseed oil no score, a 3, or a 4, is not evidence of anything except that the name split. We do not carry the 4: we identified no primary document that prints one. And safety is not the same question as comedogenicity. The Cosmetic Ingredient Review assessed Linum usitatissimum (linseed) seed oil within its 2017 review of plant-derived fatty-acid oils and concluded it safe as used in cosmetics. That is a conclusion about dermal irritation and sensitisation. It is not a comedogenicity finding, and a material can be both safe on the skin and able to clog a follicle — those are different endpoints, and the CIR review speaks only to the first.

Where you’ll see it

On a label it reads Linum Usitatissimum (Linseed) Seed Oil. In skincare it turns up in facial oils and serums sold on their omega-3 content, and in some balms and masks. It is the same botanical species as the linseed oil sold in hardware shops as a wood finish and paint binder — but that is often a chemically different product (boiled linseed oil carries metallic driers and other additives), not merely a different grade, even though the shared "drying oil" chemistry is why one plant carries both lives. Those are illustrative categories rather than a measured prevalence; we have not audited the market, and label position is not a dose.

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. Kligman AM, Kwong T. "An improved rabbit ear model for assessing comedogenic substances." Br J Dermatol 100(6):699–702 (1979) A primary rabbit-ear comedogenicity assay, independent of and earlier than Fulton 1989, on a 0-to-3 scale — sixteen materials, scored by whole-mount and by histology, with the two methods in "excellent agreement." We read its abstract, which describes the method but names no individual ingredient. We did NOT open its data table; the placement of linseed oil among its most comedogenic materials, and the score of 3, we take from a secondary review of the study rather than from the printed row. Method as reported: test materials applied for two weeks to rabbit ears just external to the ear canal.
2. Kligman AM, Mills OH. "Acne cosmetica." Arch Dermatol 106(6):843–850 (1972) The paper that coined the term "acne cosmetica" and established the rabbit-ear assay, on a 0-to-3 scale. Secondary reviews of it report linseed oil among the most comedogenic of the seven vegetable oils it tested, alongside cocoa butter and olive oil. We have not opened its data table; we cite it as the origin of the score and the scale, and we take the specific placement of linseed at second hand. Same lead author as the 1979 paper above, so the two are a replication by one group, not independent corroboration.
3. Kern D. "What Is Comedogenicity, and What Ingredients Are Comedogenic? The Full Story." Acne.org (last updated 24 March 2022) A secondary review, not a measurement: a human-written walk-through of eleven comedogenicity studies from 1968 to 2009, reproducing each study's table as a scanned image. It is the source of our identification of linseed oil's placement in the 1972 and 1979 studies, because we could not open the primary tables themselves. Cited for exactly that, and labelled as a republisher of those assays rather than an independent one. It is careful about scale — it states plainly that Kligman's studies ran 0 to 3 while Fulton's ran 0 to 5 — which is the distinction this page turns on.
4. Fulton JE. "Comedogenicity and irritancy of commonly used ingredients in skin care products." J Soc Cosmet Chem 40:321–333 (1989) The single most-quoted comedogenic table in existence, and the paper most sources wrongly credit for flaxseed oil's score. Cited here for what it does NOT contain: read row by row off a 400dpi render of the journal scan, its 220-row table has no linseed row and no flaxseed row, in any section. Its 0-to-5 scale is also the reason the Kligman 3 gets misread as middling. Cited as the source of a misattribution, not as evidence for the rating.
5. Kligman AM. "Petrolatum is not comedogenic in rabbits or humans: a critical reappraisal of the rabbit ear assay and the concept of 'acne cosmetica'." J Soc Cosmet Chem 47:41–48 (1996) The assay's own creator, decades later, arguing that his rabbit-ear model over-calls bland occlusive greases such as petrolatum. Cited as the general reason to hold the legacy tier at Low confidence. Its limits cut both ways here: it is not a retraction of the 1972 paper, and its subject is inert greases, not a reactive polyunsaturated drying oil, so it does not specifically overturn or confirm flaxseed's score. We have read secondary accounts of it and its abstract, not the full text.
6. Cosmetic Ingredient Review Expert Panel. "Safety Assessment of Plant-Derived Fatty Acid Oils as Used in Cosmetics." Int J Toxicol (2017), doi:10.1177/1091581817740569 An expert-panel safety review that includes Linum usitatissimum (linseed) seed oil and concludes the plant-derived fatty-acid oils safe as used. Cited for two narrow things: it confirms that linseed and flaxseed name one material, and it is a SAFETY conclusion (dermal irritation and sensitisation), not a comedogenicity one. We do not use a safety finding as evidence about pores.

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
• Corn Oil Caution Low
• Cottonseed Oil Caution Low
• Evening Primrose Oil Caution Low
• Grapeseed Oil Caution Low

Last reviewed 2026-07-12 · How we decide

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