Stearyl Heptanoate
Stearyl heptanoate is rated Clogging on the strength of a single number: a comedogenic 4 in Fulton's 1989 rabbit-ear assay, genuinely the material's own reading, and the only measurement of it in the corpus we searched. We found no other laboratory's reading of the same ester, and no human study of it.
Ester emollient flagged by legacy rabbit-ear assays.
What it is
Stearyl heptanoate is the ester of stearyl alcohol and heptanoic acid — an eighteen-carbon fatty alcohol capped with a seven-carbon acid. Its CAS number is 66009-41-4; the INCI name is Stearyl Heptanoate, and octadecyl heptanoate is a chemical synonym for it. The Cosmetic Ingredient Review's safety assessment and the industry portal CosmeticsInfo both describe it as a water-insoluble skin-conditioning agent and emollient, one of a family of stearyl alkanoates — alongside stearyl caprylate, palmitate, stearate, behenate and olivate — that share its structure and, when metabolised, break back down to stearyl alcohol and the corresponding fatty acid. A formulator reaches for it in the oil phase for a light, dry, non-greasy slip: the same job the cetyl esters and the isopropyl esters do, without the heavier feel of a fixed oil. It is a spreading emollient, chosen for how a product feels going on rather than for any active property.
Why we rate it Clogging
We rate it Clogging at Low confidence. The confidence is Low because the entire evidence is a single rabbit-ear assay, and we would rather say that than dress it up. The number is real, and it is this material's own. James Fulton's 1989 survey in the Journal of the Society of Cosmetic Chemists — the source of nearly every comedogenic number in circulation — gives stearyl heptanoate its own row in Table I, among the esters: a comedogenicity grade of 4 on his 0-to-5 scale. We read that row off a render of the journal scan, not off a list quoting it. By Fulton's own published key, "a minimal grade of 0 to 1 is not considered significant," 2 to 3 is "borderline," and only "a grade of 4 to 5 is uniformally reproduceable and considered positive." So the 4 sits in the one band Fulton treated as a real finding rather than noise. The row carries no asterisk, and it sits in the ester section rather than the "Oils" section, so his footnote that oil results "depend on source of raw material" does not attach to it. The method behind that 4 is the whole of the evidence, so it is worth stating plainly: the ingredient diluted to roughly 10% in propylene glycol, about 1 mL applied to the inner ear of three New Zealand albino rabbits, five days a week for two weeks, the follicles then scored for keratosis under a micrometer. Three rabbit ears in 1989 — not a human face, not a finished product, and we hold no measured in-use concentration to set beside the 10%. And unlike some of the higher ester scores, Fulton did not single this one out. His conclusion warns about "major offenders" — isopropyl myristate among the materials it names — and stearyl heptanoate is not one of them. It is a row in his table and nothing more in his prose: a positive reading, but one he neither discussed nor tried to explain. The rating rests on the row.
What the evidence doesn’t tell you
Everything here rests on one three-rabbit experiment, in one paper, in 1989. It was tested at a single concentration — roughly 10% in propylene glycol — so there is no dose-response curve. We do not have a measured in-use concentration to give you, and we are not going to invent one. We identified no other assay of stearyl heptanoate anywhere in the legacy corpus we hold. Morris and Kwan's independent 1983 rabbit-ear study — thirty-two materials, eleven of them esters, on the same 0-to-5 scale — has no stearyl heptanoate row; Fulton's own earlier 1984 rabbit paper, which we have read in full, does not test it either; and Nguyen, Dang and Maibach's 2007 rabbit-ear study names its fourteen test materials in its abstract, with stearyl heptanoate not among them. So unlike an ester where two laboratories happen to land near each other, this 4 stands or falls on a single assay, and nothing corroborates it. We identified no human comedogenicity study of stearyl heptanoate. No document we found counts comedones on a human face for it, which is what the word "comedogenic" is supposed to describe. The modern literature we have read on the ingredient is a safety assessment, not a pore study: the Cosmetic Ingredient Review panel reviewed stearyl heptanoate among the stearyl alkanoates and concluded it safe as used, finding it a mild skin irritant undiluted and not a sensitiser. A safety conclusion weighs irritation, sensitisation and toxicity — not follicular plugging — so it neither supports nor refutes the comedogenic 4, and we do not use it as either. We are not going to tell you why it would clog. The obvious move is to reach for a mechanism — that a light ester spreads into the follicle and holds keratin there — and the content mills state exactly that as fact. No comedogenicity paper we read demonstrates a mechanism for this molecule; the assay counted comedones, it did not explain them. And the assay itself has been contested for decades. Draelos and DiNardo, in 2006, tested finished products on human backs and found products testing non-comedogenic despite containing ingredients the rabbit assay had scored comedogenic; a 2025 review in JAAD Reviews found that no standardised comedogenicity test exists and that "non-comedogenic" is an unregulated label. Those objections apply to this 4 as much as to any other rabbit number, with the difference that here there is not even a second assay to set beside it.
Where you’ll see it
On a label it appears as Stearyl Heptanoate, used as an emollient and skin-conditioning agent. The Cosmetic Ingredient Review's assessment and the CosmeticsInfo portal describe it as a water-insoluble ester used across skin-care and colour-cosmetic formulations — the kinds of product it suits rather than a measured prevalence, since we have not audited the market and a label position is not a dose. The practical point is that it is one of several interchangeable dry-slip esters a formulator can reach for, and the neighbours on that shelf carry very different comedogenic numbers. The 4 belongs to this specific ester, not to the category it sits in.
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 the number, read off a render of the journal scan rather than a list quoting it. A rabbit-ear assay: the ingredient at roughly 10% in propylene glycol, 1 mL to the inner ear of three New Zealand albino rabbits, five days a week for two weeks, follicular keratosis scored under a micrometer, on a 0-to-5 scale whose own key calls 4-5 "considered positive." Table I prints "Stearyl heptanoate" at a comedogenicity grade of 4 in the ester section, with no oils footnote applying to it. It is one assay, by one author, who called his own survey "not at all definitive but simply designed to stimulate research." The lists that carry a 4 for this ingredient are quoting this row, not an independent measurement.
- 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 primary rabbit-ear assay on the same 0-to-5 scale, six years before Fulton 1989 and in a different laboratory — not a republisher of him, and on record contradicting him on other materials. Cited here for what it does NOT contain: its thirty-two rows include eleven esters, and stearyl heptanoate is not among them, so it offers no independent reading of the 4.
- Fulton JE, Pay SR, Fulton JE 3rd. "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 a 0-to-5 scale with a different threshold key from his 1989 survey, now obtained and read in full. Cited for a bounded negative: its table does not test stearyl heptanoate, so it neither confirms nor revises the 1989 grade. It is the same author, not an independent lab, and it is named here only to show the 4 is not corroborated even by Fulton's other paper.
- 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-canal study on a 0-4 scale — a third scale, and one easy to misread as Fulton's. Its abstract names all fourteen test materials, and stearyl heptanoate is not one of them. Cited for that absence: a 2007 assay that could have corroborated or revised the 1989 grade does not touch this ester.
- Fiume MM, Bergfeld WF, Belsito DV, et al. "Safety Assessment of Stearyl Heptanoate and Related Stearyl Alkanoates as Used in Cosmetics." Int J Toxicol 31(5 Suppl):141S-146S (2012) A Cosmetic Ingredient Review Expert Panel safety assessment, published in a peer-reviewed journal — cited for identity, function and safety, not for comedogenicity. It establishes that stearyl heptanoate is the ester of stearyl alcohol and heptanoic acid, a water-insoluble skin-conditioning emollient in a family of stearyl alkanoates, and that the panel judged it safe as used, a mild irritant undiluted and not a sensitiser. A safety conclusion weighs toxicity, irritation and sensitisation, not follicular plugging, so it is not evidence for or against the comedogenic rating and we do not use it as such.
- 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 human upper backs and found products testing non-comedogenic despite containing ingredients the rabbit assay had scored comedogenic. Cited because it cuts against a high rabbit-ear grade as much as a low one: an isolated ingredient's score does not transfer intact to the formula it ends up in. It is not a same-substance rabbit-versus-human validation, and we do not present it as one.
- "Comedogenicity in cosmeceuticals: a review of clinical relevance, regulatory gaps, and future directions." JAAD Reviews (2025) A recent peer-reviewed review of the field. 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 legacy number, including this one.
- Face Reality Skincare — pore-clogging ingredient list A consumer-facing republisher of the legacy scores, and one of the places a reader will have met the 4 for stearyl heptanoate. Not an independent measurement: the number it carries has no origin other than Fulton's 1989 table, the only assay of this ingredient we can trace.
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 2026-08-12 · How we decide