Porecelain

Flawless skin starts with the fine print.

Isocetyl Alcohol

Isocetyl alcohol is rated Clogging, and for once the number belongs to it: Fulton's 1989 rabbit-ear table scored isocetyl alcohol 4 on a 0-to-5 scale, a positive by his own key — but that single reading is the whole of the evidence, and no other assay in the legacy corpus we searched has a row for it.

Clogging Low confidence Legacy score 4 on a 0-5 scale · Fulton 1989 · low reliability

Branched C16 alcohol mixture; Fulton 1989 scored 4 in one three-rabbit experiment.

What it is

Not a single molecule. Isocetyl alcohol is a branched C16 isohexadecanol substance — a technical mixture registered under CAS 36311-34-9 and UNII 1800H64066, and named Isohexadecanol by CosIng and by Health Canada. The identity records list 2-hexyl-1-decanol (2-hexyldecanol) and 2-butyl-1-dodecanol among its components, which is why a supplier's synonym list and a regulator's substance record do not always print the same name. Formulators use it as an emollient, skin-conditioning agent and viscosity modifier. Where straight-chain cetyl alcohol is a waxy solid, the branched material is reported as a liquid, which is why a formulator reaches for it as a light, spreadable oil phase rather than a thickener. On a label it is Isocetyl Alcohol. That the material is a mixture rather than one defined isomer matters for a comedogenic number: Fulton records nothing about the supplier, grade or composition of the sample he scored, so the 4 belongs to whatever branched C16 alcohol arrived in his laboratory, not to a specified molecule. It should not be confused with isocetyl stearate, an ester built from this alcohol and stearic acid. That is a different material with a different — and disputed — score, and the shared word "isocetyl" is exactly the kind of near-name this site exists to keep apart.

Why we rate it Clogging

We rate it Clogging, at Low confidence, and the confidence is Low because the direct evidence is one three-rabbit experiment from 1989. That reading is James Fulton's 1989 survey in the Journal of the Society of Cosmetic Chemists. His table prints "Isocetyl alcohol" and scores it 4 for comedogenicity on a 0-to-5 scale. We render the table at 400dpi and read all 220 rows by eye, because OCR drops the numeric columns, and this row says what it appears to say. That is worth stating, because on most pages of this site it does not: coconut oil has no row, lanolin has no row, rosehip oil has no row. Isocetyl alcohol has one, and the number the charts quote for it is a measurement of it. And Fulton's own key to his own scale, which almost nobody quotes alongside the number: "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 this 4 is a positive by the standard of the man who produced it — not the borderline shrug that its straight-chain sibling's 2 is. That is the distinction the rating turns on: in the same 1989 table and under the same general protocol, cetyl alcohol scored 2, which Fulton called borderline and we rate Clear, while isocetyl alcohol scored 4, which he called positive. Fulton reports no per-row animal assignment, so "the same rabbits" would be more than the paper says; what the paper supports is one table, one protocol, two grades. The row carries no asterisk. Fulton attached a footnote — "results depend on source of raw material" — to his section VI, "Oils", and it governs every oil and butter he printed. Isocetyl alcohol sits in the alcohols section, not that one, so that particular caveat does not touch this number. There is a contrast in the table worth naming, and a line we will not cross in naming it. Fulton's straight-chain fatty alcohols cluster in the borderline band — myristyl alcohol 2, cetyl alcohol 2, cetearyl alcohol 2, stearyl alcohol 2 — while the two that reach his positive band are isocetyl alcohol, which is branched, and oleyl alcohol, which is unsaturated, both at 4. Isocetyl and cetyl alcohol are the same C16 formula in two shapes, and in Fulton's data they score two grades apart. That is the association his numbers show, and it is a description of one table rather than a validated structure-activity rule: branching and unsaturation are not established predictors of comedogenicity, and we know of no study that tested them as such. Why the branched material scored higher, we do not know: Fulton offers no mechanism in the passages we have read, and we are not going to invent one, because a made-up reason attached to a real number is the failure this site was built to name. The method behind the 4: ingredient diluted to roughly 10 percent in propylene glycol, 1 ml applied to the inner ear of New Zealand albino rabbits, three rabbits per assay, five days a week for two weeks, follicular keratosis measured with a micrometer. Fulton called the survey itself "not at all definitive but simply designed to stimulate research".

What the evidence doesn’t tell you

One rabbit-ear assay, from 1989, is the entire direct evidence — and it is the same assay we discount everywhere else on this site. The reasons do not stop applying because the result this time is a positive rather than a borderline. Draelos and DiNardo argued in 2006, testing finished products on human backs, that rabbit-ear scores do not reliably transfer to human skin; the 2025 JAAD Reviews survey found that no standardised comedogenicity test exists and that "non-comedogenic" is an unregulated claim. Those are the grounds on which we refuse to trust the 4s elsewhere, and they apply to this one. No independent replication under this exact printed name was identified in the corpus we hold or the searches we ran. Among the legacy papers — Fulton's own 1984 survey, Morris and Kwan 1983, Nguyen, Dang and Maibach 2007, the Kligman papers, Lanzet, and Kanaar — none tested isocetyl alcohol. Fulton 1984 scored oleyl alcohol 4 but has no isocetyl alcohol row at all, so the number has no second Fulton reading behind it. Morris and Kwan's thirty-two rows do not include it. Nguyen's fourteen materials include isocetyl stearate, cetyl alcohol and stearyl alcohol, but not isocetyl alcohol. So the 4 has been neither confirmed nor contradicted by any other paper; it stands alone, which is a weaker thing than a number several laboratories agree on. We identified no study that counted comedones on human skin after applying isocetyl alcohol. Safety reviews of the ingredient, and of the esters built on it, assess toxicity, irritation and sensitisation rather than follicular plugging, and safety is not noncomedogenicity. The exposure the assay used is not the exposure a product delivers. Roughly 10 percent in propylene glycol, applied five days a week for two weeks to a rabbit's ear, is a long way from a light emollient at whatever fraction a real formula contains, and Draelos's argument is precisely that the distance between the two is where the score stops predicting. Finally, the consumer charts that print a 4 for isocetyl alcohol — Banish among them — are quoting this one 1989 assay; the article says so itself. Matching numbers across several charts is not several measurements agreeing. It is one measurement, reprinted.

Where you’ll see it

On a label it appears as Isocetyl Alcohol. Because it is a liquid emollient rather than a thickening wax, industry directories describe it turning up where a light, spreadable oil phase is wanted — colour cosmetics, sunscreens, lotions, hair products — but those are illustrative categories drawn from supplier descriptions, not a measured prevalence, and we have not audited the market. Keep it apart from two neighbours it is easily confused with: cetyl alcohol, its straight-chain isomer, which carries a different number and a different rating; and isocetyl stearate, the ester made from it, which carries a different number again.

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 the score, and of nearly every comedogenic number in circulation. Read off a 400dpi render of the journal scan rather than from a list quoting it, because OCR drops the numeric columns. Method: ingredient at roughly 10% in propylene glycol, 1 ml to the inner ear of New Zealand albino rabbits, three rabbits per assay, five days a week for two weeks, follicular keratosis measured with a micrometer; scale 0 to 5. Isocetyl alcohol appears among the alcohol rows of his table, scored 4. What it cannot support: Fulton calls the survey "not at all definitive but simply designed to stimulate research", warns the rabbit ear is so sensitive that "not everything that irritates this model will also irritate human skin", and defines his own grades so that 4 to 5 is "considered positive". It is one three-rabbit experiment in one laboratory, at a concentration and under a dosing regime no product reproduces. He records nothing about the supplier or composition of the branched C16 alcohol he tested.
  2. 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, now read in full off the journal scan. Cited here for what it does NOT contain: it scores oleyl alcohol 4 but has no isocetyl alcohol row, so the 1989 reading has no second Fulton measurement standing behind it. A reminder that "Fulton scored it" here means one paper, once.
  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 other major rabbit-ear survey, six years before Fulton and on the same 0-to-5 scale, undiluted material unless stated, three rabbits, 14 applications, microscopic grading. Cited for what its thirty-two rows do NOT include — isocetyl alcohol is not among them — and to keep two near-names apart: Morris and Kwan tested isocetyl STEARATE, a different molecule, and scored it 0 to 1. They also contradict Fulton in print on other materials, which is why one Fulton reading cannot be read as "the literature agrees".
  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-to-4 scale, abstract read via EuropePMC; the full text and its per-material scores were not read, so no number is carried from it. Cited for what its fourteen test materials do NOT include: isocetyl stearate, cetyl alcohol and stearyl alcohol appear; isocetyl alcohol does not. It neither confirms nor disputes the 4.
  5. SpecialChem, INCI directory entry for Isocetyl Alcohol A commercial cosmetic-ingredient reference directory, cited for the function description on this page: the emollient, skin-conditioning and viscosity-modifying roles, and the liquid physical form. It is trade reference material, not a study; it says nothing about comedogenicity and is not cited as evidence for the rating. Where its synonym list and the regulatory substance records disagree on composition, we follow the substance records.
  6. Substance identity records for Isohexadecanol / Isocetyl Alcohol: CAS 36311-34-9, UNII 1800H64066; EU CosIng and Health Canada Cosmetic Ingredient Hotlist entries under the name Isohexadecanol Regulatory and identity references, not studies. Cited for one point only, and it is the point that governs how the score should be read: the INCI name covers a branched C16 isohexadecanol substance — a technical mixture whose identity records list 2-hexyl-1-decanol and 2-butyl-1-dodecanol among its components — rather than a single defined isomer of cetyl alcohol. What they cannot support: anything about comedogenicity, which they do not address.
  7. Draelos ZD, DiNardo JC. "A re-evaluation of the comedogenicity concept." J Am Acad Dermatol 54(3):507-512 (2006) A "Current Issues and Opinion" piece, not a same-substance rabbit-versus-human validation. It tested finished products on human upper backs and argued that an isolated ingredient's rabbit-ear score does not reliably predict what a finished formula does on skin. Cited against our own rating as much as for it: it is a reason the confidence here stays Low despite the score being a positive.
  8. "Comedogenicity in cosmeceuticals: a review of clinical relevance, regulatory gaps, and future directions." JAAD Reviews (2025) A recent peer-reviewed narrative review covering the literature from 1972 to 2025. Finds that no standardised comedogenicity test exists and that the "non-comedogenic" claim is unregulated. A synthesis, not new data; cited for the field-wide caveat that applies to every rabbit-ear number, including this one.
  9. Banish, "The Ultimate Guide to Acne-Causing Ingredients" A commercial acne-brand ingredient list, and the place a reader is most likely to have met the 4 for this ingredient. It is a republisher of the Fulton 1989 rabbit-ear lineage — the article says as much — not an independent measurement. Cited to characterise where the number circulates, not as corroboration of it.

Others in the same family

Fatty alcohols 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 fatty alcohols as a family ›

Last reviewed 2026-08-05 · How we decide

‹ Check a full ingredient list