Porecelain

Flawless skin starts with the fine print.

Evening Primrose Oil

Evening primrose oil carries a comedogenic 3, and for once the number belongs to the material named: Fulton's 1989 rabbit assay printed a row for evening primrose oil itself, not a neighbour or a derivative. What the charts drop is that a 3 was borderline on Fulton's own scale, that it comes from one rabbit-ear experiment using three rabbits, and that the oil sits in the section he footnoted "results depend on source of raw material." We rate it Caution at Low confidence.

Caution Low confidence Legacy score 3 on a 0-5 scale · Fulton 1989 · low reliability

Fulton 1989 scored 3 — borderline by his own key — in one three-rabbit experiment.

What it is

The oil pressed from the seeds of Oenothera biennis, a North American plant in the evening-primrose family (Onagraceae). Despite the name it is not a rose, and it is the only entry anywhere in Fulton's 220-row table in which the letters "rose" appear at all. On a label it reads Oenothera Biennis Oil, or simply Evening Primrose Oil. Formulators and supplement makers reach for it for two polyunsaturated fatty acids it is unusually rich in. Its dominant fatty acid is linoleic acid, a peer-reviewed review by Eskin puts the seed oil at roughly 65 to 75% linoleic, with gamma-linolenic acid (GLA) as a minor but marketable component, commonly around 8 to 10%; the remainder is largely oleic and palmitic acid. GLA is the reason it is sold as an oral supplement and folded into "barrier" and soothing skincare. It is a light, fast-absorbing liquid oil used as an emollient and skin-conditioning agent.

Why we rate it Caution

We rate it Caution at Low confidence, and the confidence tier is the honest part: everything below rests on a single rabbit-ear reading from 1989. Start with what is unusual about this page. The comedogenic 3 that follows evening primrose oil around actually belongs to evening primrose oil. Fulton's 1989 survey, Table I, section VI, "Oils," prints the row "Evening primrose oil — 3." Not a differently-processed grade, not a glyceride, not a neighbouring plant read off the wrong line, which is how most of the numbers this site examines turn out to be attached to something the paper never tested. Here the row says evening primrose oil, and evening primrose oil is what the rating covers. That is worth saying plainly, because it is rare. What the 3 is worth is a separate question, and Fulton answered it himself. He printed his own 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." A 3 is the top of his borderline band: by his key it is neither "not significant" nor "uniformally reproduceable and considered positive." The lists that reprint it as a flat "3 — moderate — avoid" have dropped the word he attached to it, which was borderline. The method, stated plainly, because it is the whole of the evidence: the ingredient diluted to roughly 10% in propylene glycol, about 1 ml applied to the inner ear of New Zealand albino rabbits, three rabbits, five days a week for two weeks, the follicles then scored for keratosis under a micrometer. A rabbit's ear, not a human face; a 10% dilution, not a finished product. And there is an asterisk, which the row does not carry but the section does. Fulton's heading reads "VI. Oils*," and he defines that asterisk once in the paper: "results depend on source of raw material." It governs every oil and butter row he printed, evening primrose included. So the 3 is not merely a borderline rabbit reading; it is a borderline rabbit reading of one unstated sample of an oil whose composition shifts with its origin. Fulton recorded no supplier, no grade, no refinement. Is there a second opinion anywhere? We did not find one. Morris and Kwan's 1983 survey is the other independent rabbit-ear study on the same 0 to 5 scale — genuinely independent, an earlier laboratory that contradicts Fulton in print on other materials rather than copying him — and it tested nine vegetable oils. Evening primrose oil is not among them. No other numeric assay we hold contains it either, and no independent replication under this exact printed name was identified in the corpus we hold or the searches we ran. So the published comedogenic record we could assemble for this oil is one borderline 3, from a single 1989 rabbit-ear experiment using three rabbits, on a sample of unstated origin. That is why the rating is Caution at Low confidence and not anything firmer.

What the evidence doesn’t tell you

What the evidence does not tell you, which on this ingredient is most of it. One study, one species, one dilution. Everything in the rating above is three rabbits' ears in 1989. We identified no study that counted comedones on human skin after applying evening primrose oil, topically, at any concentration. The rabbit-ear model that produced the number has itself been questioned for decades: Draelos and DiNardo (2006) tested finished products on human backs and found the assay a poor guide to what a formula does on a person, though they did not re-test this oil; and a 2025 review in JAAD Reviews found that no standardised comedogenicity test exists at all and that "non-comedogenic" is an unregulated label. Those objections bear on a borderline 3 exactly as much as on anyone's 4. There is human evidence about evening primrose oil and skin, and it is the wrong evidence for this question — worth naming precisely so it is not mistaken for an answer. The study usually cited, Muggli 2005, gave the oil by mouth: soft-gel capsules, 3 × 500 mg twice daily for twelve weeks, in healthy adults, measuring skin moisture, transepidermal water loss, elasticity, firmness and roughness. It counted no comedones and it was never applied to skin. Oral supplementation is not topical application, and improved moisturisation is not the absence of follicular plugging. None of it tells you what the oil does inside a pore. Safety is not comedogenicity. The Cosmetic Ingredient Review assessed evening primrose oil within its group of plant-derived fatty acid oils and concluded the group safe as used, on the strength of a history of food use, the oils' composition, and evidence that they were not dermal irritants or sensitisers. That is a finding about irritation and allergy. An oil can be non-irritating and non-sensitising and still keratinise a follicle; irritation, sensitisation and comedogenicity are three different endpoints, and the CIR measured the first two. Finally, the composition and the rabbit point different ways, and we found nothing that resolves them on human skin. Evening primrose oil is among the more linoleic-rich oils on any label, and high-linoleic oils are widely assumed to sit easier on acne-prone skin — part of why the oil is recommended for it. Fulton's rabbit did not read it that way. We are not going to reconcile the two for you with a mechanism: the one thing that would settle it — this oil, on a human face, with comedones counted — is not in the record we searched.

Where you’ll see it

On a label it appears as Oenothera Biennis Oil, sometimes as Evening Primrose Oil. It turns up in facial oils and serums, moisturisers and balms, and in soothing or "barrier-support" products that lean on its GLA content, and it is sold very widely as an oral supplement — which is where most of its human study history actually sits, and why so much of what is written about it concerns swallowing it rather than wearing it. We have not audited its prevalence or a typical use concentration and will not guess at either; where it sits on an ingredient list 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. Fulton JE. "Comedogenicity and irritancy of commonly used ingredients in skin care products." J Soc Cosmet Chem 40:321–333 (1989) The primary source, and the origin of nearly every comedogenic number in circulation — read here off a 400dpi render of the journal scan rather than via a list quoting it. A rabbit-ear assay: ingredient at roughly 10% in propylene glycol, applied to the inner ear of three New Zealand albino rabbits, five days a week for two weeks, follicular keratosis scored under a micrometer. Table I, section VI ("Oils*"), prints "Evening primrose oil — 3" — a row under the exact printed name of the material this page is about, which is unusual. Fulton's own key defines a 3 as borderline (0–1 "not significant," 2–3 "borderline," 4–5 "positive"), and the section asterisk means "results depend on source of raw material," applying to every oil row including this one. He records no supplier, grade or refinement for the sample.
  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) The other independent primary rabbit-ear assay on the same 0–5 scale, six years before Fulton 1989 and openly contradicting him in print on other materials — so not a republisher of him. Cited here for what it does NOT contain: it tested nine vegetable oils (olive, avocado, castor, corn, sesame, safflower, peach kernel, grape seed, sweet almond) and evening primrose oil is not one of them. It is the reason we can say the oil has no independent second reading: the one survey that could have corroborated Fulton simply never tested it.
  3. 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) Fulton's earlier rabbit-ear survey, read in full off the journal scan: two New Zealand albino rabbits per test, one ear dosed daily for two weeks, the alternate ear as control, on a 0–5 scale whose key differs from the 1989 one — there, 1 to 2 is not significant and 3 or above is considered positive. Cited for an absence: it has no evening primrose oil row, so his own earlier work does not corroborate the 1989 reading.
  4. Nguyen SH, Dang TP, Maibach HI. "Comedogenicity in rabbit: some cosmetic ingredients/vehicles." Cutan Ocul Toxicol 26(4):287–292 (2007) A later rabbit-ear assay on a 0–4 scale; abstract read via EuropePMC, full text and per-material scores not read, so no number is carried from it. Cited for an absence: its fourteen named test materials are esters, fatty alcohols, a sulfate, cocoa butter, paraffin and petrolatum, and evening primrose oil is not among them.
  5. Burnett CL, Fiume MM, Bergfeld WF, et al. (Cosmetic Ingredient Review Expert Panel). "Safety Assessment of Plant-Derived Fatty Acid Oils." Int J Toxicol 36(3 Suppl):51S–129S (2017) A SAFETY review of 244 plant-derived fatty acid oils by the Cosmetic Ingredient Review Expert Panel, evening primrose oil among them (the peer-reviewed journal version, not a comment-stage CIR draft). The panel is convened and funded through the industry's trade association, so it is expert and published but not structurally independent of the sector whose ingredients it reviews; we cite it as such rather than as an outside check. It concluded the group safe as used, on a history of food use, the oils' composition, and data showing they were not dermal irritants or sensitisers. Cited to make one distinction: this assesses irritation and sensitisation, not comedogenicity. Safety is not the same endpoint as follicular plugging, and the report makes no comedogenic claim about this oil.
  6. Eskin NAM. "Borage and evening primrose oil." Eur J Lipid Sci Technol 110(11):1057–1063 (2008) A peer-reviewed lipid-chemistry review, cited only for the fatty-acid composition on this page: linoleic acid dominant at roughly 65–75%, gamma-linolenic acid a minor component around 8–10%. Nothing to do with pores; a composition claim needs a composition source, and this is one.
  7. Muggli R. "Systemic evening primrose oil improves the biophysical skin parameters of healthy adults." Int J Cosmet Sci 27(4):243–249 (2005) The human study most often cited for "evening primrose oil and skin," characterised carefully so it is not mistaken for a comedogenicity result. It gave the oil ORALLY — soft-gel capsules, 3 × 500 mg twice daily for twelve weeks — to healthy adults, and measured skin moisture, transepidermal water loss, elasticity, firmness, fatigue resistance and roughness. It counted no comedones and applied nothing to the skin. Systemic supplementation is not topical use, and moisturisation is not the absence of pore-clogging.
  8. 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 in JAAD that tested finished products on small human panels and found products testing non-comedogenic despite containing ingredients the rabbit assay had scored as comedogenic. Cited for the general caveat about the rabbit-ear model; it did not test evening primrose oil, and it is a critique of the method, not a re-reading of this row.
  9. "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. Finds that no standardised comedogenicity test exists and that "non-comedogenic" is an unregulated label. 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. Cited for the field-wide caveat that applies to a borderline 3 as much as to any higher score.

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 2026-08-05 · How we decide

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