Porecelain

Flawless skin starts with the fine print.

Decyl Oleate

Decyl oleate is rated Clogging, and for once the number attached to it is the one the labs actually printed. Three rabbit-ear assays — Morris and Kwan 1983, Fulton 1984 and Fulton 1989 — all scored it 3 on a 0-to-5 scale, and a fourth study, Nguyen, Dang and Maibach 2007, put it in the positive column on a different scale. Most pages here exist because a score is wrong. This one exists because the score is unusually well corroborated, and because that same 3 is called positive in one of Fulton's papers and borderline in the other.

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

Printed 3 of 5 by Fulton 1989, Fulton 1984 and Morris and Kwan — positive on 1984's key, borderline on 1989's.

What it is

Decyl oleate is an ester — the reaction product of decyl alcohol (a straight, ten-carbon fatty alcohol) and oleic acid (the eighteen-carbon fatty acid that makes up most of olive oil). The Cosmetic Ingredient Review's report on decyl and isodecyl oleates describes them in exactly those terms, as esters of oleic acid. In a formula it is an emollient and a spreading oil: a light, non-greasy liquid used to give a lotion or a colour cosmetic its slip and to dissolve oil-phase ingredients. On a label it is Decyl Oleate. One neighbour is worth naming now, because conflating the two is the easiest mistake to make here. ISODECYL OLEATE is a different ingredient — the same oleic acid esterified to a branched (iso-)decyl alcohol rather than a straight one. It has its own rows in the same tables, and they do not read the same: Fulton's 1989 table scores isodecyl oleate 2-3*, with his asterisk meaning "results depend on source of raw material," and Morris and Kwan scored it 1 on the same 0-to-5 scale. The straight-chain material on this page is the one that scored 3, unasterisked, three times.

Why we rate it Clogging

We rate it Clogging, at Low confidence, and the two halves of that sentence are pulling in opposite directions on purpose. The number holds up, which is rare on this site. Most Porecelain pages exist because a circulating score traces to the wrong molecule, to a user comment, or to nothing at all. Decyl oleate is the opposite case. Morris and Kwan, in the Journal of the Society of Cosmetic Chemists in 1983, printed "Decyl Oleate — 3" on a 0-to-5 scale. Fulton, Pay and Fulton, in the Journal of the American Academy of Dermatology in 1984, printed "Decyl oleate — 3" on the same scale, with no asterisk, and named decyl oleate outright in their abstract's list of ingredient offenders, alongside isopropyl myristate and myristyl myristate. Fulton's own 1989 survey, the table from which nearly every comedogenic number in circulation descends, printed 3 again, no asterisk and no range. We read all three off transcriptions of the printed tables, not off a list quoting them. It is the same ingredient name each time, and the answer does not move. Two laboratories, not three. It is worth being exact about who those three readings belong to, because we previously overstated it here. The 1984 and 1989 papers are both James Fulton's — a second experiment by the same investigator, five years apart, not an independent replication. The genuinely independent 0-to-5 reading is Morris and Kwan's, and it matters more for that. Their paper spends part of its length contradicting Fulton in print: they graded sodium lauryl sulfate 0 at both 5% and 10% in water, and wrote that their finding "conflicts with the high scores published by Fulton et al." (Fulton's own sodium lauryl sulfate readings do not agree with each other either — his 1984 table prints 5, and his 1989 table has no row for it at all — which is a different page's problem.) On decyl oleate, a lab willing to say that in print returned his number anyway. There is a fourth study, and it is the second independent one. Nguyen, Dang and Maibach, "Comedogenicity in rabbit: some cosmetic ingredients/vehicles," Cutaneous and Ocular Toxicology 26(4):287-292 (2007). Its abstract lists the materials tested, in order: 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. Then one sentence: "The first nine were deemed positive." Decyl oleate is the fifth name on that list. We have read that abstract and not the table behind it, so we carry no number from it and we will not invent one — it uses a 0-to-4 scale, not Fulton's, and a number we have not read is a number we do not print. What it establishes is narrower than a score and still enough to matter: a third laboratory, twenty-four years after Morris and Kwan, put this exact material in its positive column. Now the part that decides the rating, and it is not the size of the number. It is that the same 3 gets two different verdicts from the same author. Fulton published a key for reading his 1989 numbers: 0-1 "is not considered significant," 2-3 is "borderline," and only 4-5 is "uniformally reproduceable and considered positive." By that key, decyl oleate's 3 sits at the top of the borderline band, one grade below the materials Fulton called reproducibly comedogenic — isopropyl palmitate at 4, and isopropyl myristate at 5, which is less a reading than the ruler, since Fulton defined grade 5 as comedones "similar to those induced by ... our standard 'positive' testing agent, isopropyl myristate." But his 1984 paper prints a different key for the same 0-to-5 scale: "a minimal grade of 1 to 2 is not considered significant. However, a grading score of 3 or above is uniformly reproducible and considered positive." By that key, the identical reading is positive. Neither key is the "real" one; each belongs to its own paper, and a bare "decyl oleate is a 3" hides that its own author classified that grade both ways. So the rating rests on this, and not on an analogy to its ester neighbours. Three papers print 3 out of 5 for the exact name. Two of the four studies that tested it — Fulton 1984 by its own threshold, Nguyen and colleagues by their own classification — treat that result as positive. One, Fulton 1989, treats it as borderline. Morris and Kwan print the number without any interpretation key we have read, so we do not put a verdict in their mouths; in their own table a 3 sits alongside isopropyl palmitate and sweet almond oil, and well above their isodecyl oleate 1. Nothing in the record reads it as inert. That is why the rating is Clogging rather than Caution. The Low confidence is a statement about what kind of evidence this is, not a doubt about the readings, and a reader should hold "borderline in his later paper" in mind alongside it, not a picture of a pore packed shut.

What the evidence doesn’t tell you

Everything above happened in a rabbit's ear, and nowhere else. The four studies are also four different protocols, which is why they are not four measurements of one thing. Morris and Kwan used the rabbit ear canal, three rabbits, materials applied undiluted unless their table says otherwise, fourteen applications, microscopic grading. Fulton's 1984 paper used two New Zealand albino rabbits per test, one ear dosed daily for two weeks and the alternate ear the control; its decyl oleate row carries no asterisk, and by that paper's own footnote an unasterisked liquid or soft solid was used "as is" rather than diluted. Fulton's 1989 survey used roughly 10% in propylene glycol on the inner ear of three rabbits, five days a week for two weeks, with follicular keratosis then scored under a micrometer. Nguyen and colleagues' method we have not read. Four concordant readings of variants of one animal model are still readings of that model, not four routes to the answer. Nor can we say the four papers tested the same stuff. They all use the exact name Decyl Oleate, which is the important part and the part most charts get wrong. But none of the documents we hold names a supplier, a lot, a purity, a residual free-oleic-acid figure or an oxidation state, so whether any two of them ran the same commercial grade is unestablished. "Same name" is what the record supports; "same material" is more than it supports. We identified no human comedogenicity study of decyl oleate. No cyanoacrylate follicular-biopsy trial, no back-panel study, nothing measuring what this ester does on a human face or in a human pore. That is the precise claim, and the precision matters: the concordant 3 has never been checked against the organism the rating is for. The rabbit-ear assay has been contested for decades. Draelos and DiNardo's 2006 piece in the Journal of the American Academy of Dermatology — a "Current Issues and Opinion" article, not a controlled trial — tested finished products on small human upper-back panels and found products that tested non-comedogenic despite containing ingredients the rabbit assay had scored comedogenic. It is evidence that an isolated ingredient's rabbit score is a poor predictor of what a finished formula does on skin; it is not a same-substance rabbit-versus-human retest of decyl oleate, and we do not present it as one. A 2025 review in JAAD Reviews concluded that no standardised comedogenicity test exists at all and that the label "non-comedogenic" is unregulated. Those objections cut against a reproduced 3 exactly as hard as they cut against anyone's 4 or 5: reproducing a measurement three times does not repair the model producing it. Concentration is a further gap the score cannot speak to. The assays used the neat material or roughly 10%, while the CIR's report on decyl and isodecyl oleates recorded decyl oleate in use "at concentrations ranging from ≤0.1 to > 50%" — a use survey from the early 1980s, not a current market figure, and a rabbit-ear grade at 10% is silent about how the same ester behaves at a fraction of a percent in an actual product. And the CIR's conclusion that decyl oleate is safe as used is a judgement about safety, not about comedogenicity — the two are different questions, we found no comedogenicity grade anywhere in its assessments, and a safety clearance is not a finding that it does not clog.

Where you’ll see it

Decyl oleate is a general-purpose emollient, so it turns up in leave-on skincare and colour cosmetics — moisturisers, sunscreens, foundations, lipsticks, cleansing oils — wherever a formulator wants light slip and an oil-phase solvent. We have not audited its market share, and label position is not a dose, so treat that as the categories it suits rather than a measured prevalence. The one concentration figure we can cite is the CIR's, from its report on decyl and isodecyl oleates: decyl oleate used "at concentrations ranging from ≤0.1 to > 50%," against isodecyl oleate's "> 0.1-25%". That is a reported use range from the early 1980s, carried forward in the panel's later alkyl-ester work, and it will not tell a reader which end of it they are looking at. The one thing worth checking on a label is the spelling. "Decyl Oleate" is the material on this page, scored 3 of 5. "Isodecyl Oleate" is the branched cousin, scored lower in both papers that tested it — 1 of 5 by Morris and Kwan in 1983, 2-3* of 5 by Fulton in 1989. They sit near each other alphabetically, and the CIR assessed them together "because of both the chemical similarity of these compounds and the similarity of the available animal and human data," but they are not the same ingredient and they did not get the same number.

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 nearly every comedogenic score in circulation, read here off a 400dpi transcription of the printed Table I rather than via a list quoting it. Method: ingredient 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 scored under a micrometer; scale 0-5. Its row for the exact material reads "Decyl oleate — 3" (no asterisk, no range), and a separate row reads "Isodecyl oleate — 2-3*", the asterisk being Fulton's footnote "results depend on source of raw material." This paper's own key defines 0-1 as not significant, 2-3 as borderline and 4-5 as positive, so under it the 3 is a borderline reading — but that key is this paper's, not his 1984 paper's. Fulton called the survey "not at all definitive but simply designed to stimulate research." A rabbit-ear assay, not a human study.
  2. Fulton JE, Pay SR, Fulton JE III. "Comedogenicity of current therapeutic products, cosmetics, and ingredients in the rabbit ear." J Am Acad Dermatol 10:96-105 (1984) The same lead author, five years earlier, in a different journal, on the same 0-to-5 scale — read in full from a 400dpi transcription of Table I. It prints "Decyl oleate — 3", unasterisked, under the heading "Surfactants and detergents", which is where the 1984 table files it rather than with the esters; by the paper's own concentration footnote an unasterisked liquid or soft solid was used "as is" rather than diluted, so this is not the 1989 paper's 10%-in-propylene-glycol preparation. Its abstract names decyl oleate explicitly in a list of ingredient offenders "such as isopropyl myristate and its analogs … myristyl myristate, decyl oleate …". Its grade key also differs from 1989's: "a minimal grade of 1 to 2 is not considered significant. However, a grading score of 3 or above is uniformly reproducible and considered positive." So the two papers agree on the number and disagree on what it means. This is NOT independent corroboration — James Fulton led both studies, and we previously described it as independent, which was wrong. Method: two rabbits per test, one ear dosed daily for two weeks, alternate ear the control. Still a rabbit-ear assay.
  3. 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 independent primary assay on the same 0-to-5 scale, six years before Fulton 1989 and in a different laboratory — not a republisher of him. Rabbit ear canal, three rabbits, materials applied undiluted unless the table states otherwise, fourteen applications, microscopic grading. It prints "Decyl Oleate — 3" and "Isodecyl Oleate — 1". We hold no interpretation key from this paper, so we report its number and do not attribute a positive/borderline verdict to it. It matters extra here because it openly contradicts Fulton elsewhere — it graded sodium lauryl sulfate 0 at 5% and at 10% in water and wrote that this "conflicts with the high scores published by Fulton et al." — which makes its agreement on decyl oleate the agreement of a willing dissenter rather than an echo. Still a rabbit ear, still one reading, and it names no supplier or grade.
  4. Nguyen SH, Dang TP, Maibach HI. "Comedogenicity in rabbit: some cosmetic ingredients/vehicles." Cutan Ocul Toxicol 26(4):287-292 (2007) A fourth rabbit-ear study, from a third research group, on a 0-to-4 scale. WE HAVE READ ONLY ITS ABSTRACT — the full text is behind a paywall — and the abstract is what carries the finding: it lists fourteen test materials in order, with decyl oleate fifth, and states "The first nine were deemed positive." We therefore carry NO number from this paper: not a score, not a concentration, not a vehicle, and its 0-to-4 scale is not comparable to Fulton's 0-to-5 in any case. What it establishes is that a later, independent primary assay placed this exact material in its positive column. Abstract read from the US EPA's HERO bibliographic record (HERO ID 1616835), which reproduces it in full, because the publisher's page is behind a challenge screen. Obtaining the table remains an open job.
  5. Cosmetic Ingredient Review Expert Panel. "Final Report on the Safety Assessment of Decyl and Isodecyl Oleates." J Am Coll Toxicol 1(2):85-95 (1982) The CIR's dedicated report on this ester and its branched cousin, cited for three narrow things and no more: the identity ("Decyl Oleate and Isodecyl Oleate are esters of oleic acid"), the reported use concentrations ("Decyl Oleate is used in cosmetic products at concentrations ranging from ≤0.1 to > 50%. Isodecyl Oleate is used at concentrations of > 0.1-25%"), and the panel's conclusion of safe as used. It is a SAFETY assessment — acute toxicity, irritation, sensitisation — not a comedogenicity study, and we found no comedogenicity grade in it. Its use figures are an early-1980s survey and are not a current market measurement.
  6. Fiume MM, Heldreth BA, Bergfeld WF, et al. "Safety Assessment of Alkyl Esters as Used in Cosmetics." Int J Toxicol 34(2 Suppl):5S-69S (2015) The published, final journal version of the CIR's assessment of the alkyl esters — not a comment-stage draft. Cited only to show what the panel currently holds for this ingredient: it carries the earlier decision forward, recording decyl oleate as "Safe as used (1982; reaffirmed in 2003)". A safety clearance is a judgement about toxicity, irritation and sensitisation, not about follicular plugging, and the two questions are separate.
  7. 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 — not a controlled trial — that tested finished products on small human upper-back panels and found products testing non-comedogenic despite containing ingredients the rabbit assay had scored comedogenic. Cited because it cuts against a reproduced 3 as much as against any alarming number: it is evidence that an isolated rabbit-ear ingredient score is a weak guide to a finished formula on human skin. It is not a head-to-head human retest of decyl oleate, and we do not present it as one.
  8. "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 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. Cited for the field-wide caveat that no standardised comedogenicity test exists and that "non-comedogenic" is an unregulated label — the caution that governs every number on this page, the corroborated ones included.

Others in the same family

Esters 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 esters as a family ›

Last reviewed 2026-08-01 · How we decide

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