Isopropyl Palmitate

Isopropyl palmitate is rated Clogging, and unlike its constant lookalike isopropyl myristate — whose comedogenic 5 is the scale's own calibration point, the reference response Fulton defined the top of his scale by — its 4 is a graded reading measured against that scale, printed by Fulton in 1989 and matched by a different laboratory six years earlier at 3. Both are rabbit assays; neither is a human face.

What it is

Isopropyl palmitate is the isopropyl ester of palmitic acid, the sixteen-carbon saturated fatty acid. On a label it is Isopropyl Palmitate, sometimes abbreviated IPP; its CAS number is 142-91-0. A formulator reaches for it as a light emollient: it thins heavier oils, cuts greasiness, leaves a dry slip rather than a film, and is used as a pigment-wetting agent and a solvent. It is also documented as a skin-penetration enhancer, which is a property of the molecule and not, on its own, a statement about pores. It is worth being exact about one thing, because the confusion below is the whole reason this page is separate. Isopropyl palmitate is not isopropyl myristate. Myristic acid is the fourteen-carbon fatty acid; palmitic is sixteen. They are two esters, two carbons apart in the chain, with two CAS numbers, and they sit next to each other on labels and in every comedogenic chart. One of them is the material the whole 0-to-5 scale was calibrated against. The other — this one — was simply measured on it.

Why we rate it Clogging

We rate it Clogging at Low confidence, because the evidence is the legacy rabbit-ear assay and nothing stronger. What the page exists to add is what kind of number the 4 actually is. Start with the sibling, because it is where the value is. Isopropyl myristate carries a comedogenic 5, the maximum, and it is the single most quoted comedogenic number in skincare. But that 5 is the scale's calibration point, not an independent result. Fulton defined the top of his scale by the response it produces: "Grade 5 is the presence of large comedones throughout the ear, similar to those induced by the application of our standard 'positive' testing agent, isopropyl myristate" — and isopropyl myristate duly sits at 5 in his table. It is the reference material: a real and reproducible response, but a circular one, because the scale was anchored to it. So when a chart hands you "isopropyl esters are a 5," it is repeating a calibration, not citing an independent finding. Isopropyl palmitate is the neighbour that was graded against that scale and returned a high reading of its own. Where the number comes from. James Fulton's 1989 survey in the Journal of the Society of Cosmetic Chemists is the source of nearly every comedogenic score in circulation, and we read its Table I off a render of the journal scan rather than a list quoting it. Among the esters it prints a row for isopropyl palmitate: comedogenicity grade 4, on a 0-to-5 scale — and his earlier 1984 survey, now read in full, scores it 4 as well, the same author agreeing with himself five years apart. On 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 he treated as a real finding rather than noise. The row carries no asterisk, which matters here: the asterisk Fulton attached to his oils — "results depend on source of raw material" — does not attach to this ester, so the usual escape hatch for a high oil score is not available for this one. A second reading, and it is genuinely independent. Morris and Kwan, in 1983 — six years before Fulton, in a different laboratory, on the same 0-to-5 scale — ran their own rabbit-ear assay and scored isopropyl palmitate 3, applied undiluted. It is not the same number as Fulton's 4, and we are not going to round the two into a single verdict they do not jointly print. What the two labs agreed on is direction: both put this exact ester, named the same way, above the noise band — Fulton's 4 in his positive band, Morris and Kwan's 3 in the borderline band just below it. And a third rabbit-ear study points the same way: Nguyen, Dang and Maibach's 2007 assay, on a 0-to-4 scale, lists isopropyl palmitate among the materials it deemed positive. We have not read its printed table, so we carry no number from it — but its verdict is not reassuring. Three assays in that direction is more corroboration than most numbers on this site can claim, which is why the rating is well supported even though the confidence is Low. So the rating is Clogging, and the honest account of the evidence is this: two rabbit-ear assays we read in full scored isopropyl palmitate 4 and 3 on a 0-to-5 scale, a third deemed it positive on a 0-to-4 scale, and none of them tested a human face, a finished formula, or a concentration anyone actually wears. The Low confidence is a statement about that gap.

What the evidence doesn’t tell you

Everything above rests on rabbit ears. Fulton's method: 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, follicles then scored for keratosis under a micrometer. Morris and Kwan ran a rabbit-ear assay too, on the ear canal, applying the material undiluted and on their own application schedule; Nguyen and Maibach's 2007 assay was a third rabbit-ear model, on a 0-to-4 scale. Fulton said plainly that the rabbit ear is more sensitive than human skin, and warned that "not everything that irritates this model will also irritate human skin." It is not a human face, not a finished product, and not an in-use dose. Concentration is doing work the bare number hides, and it cuts both ways. These assays test at high strength — Fulton at about 10%, Morris and Kwan undiluted — and a comedogenic grade is a property of a material at a dose, not a fixed trait it carries into a 3% emollient. But the author who produced the 4 distrusted exactly that reassurance: his conclusion reads, "We are not convinced of the statement that lower concentrations of these compounds can be safely used with no comedogenic consequences," and it names isopropyl myristate specifically among the "major offenders" it is warning about. That is a caveat pointing both ways at once: against assuming a low percentage is automatically safe, while conceding that the safe threshold was never established. We are not going to tell you why it clogs. The obvious temptation is to reach for a mechanism — that the ester spreads into the follicle and traps sebum — and the content mills state exactly that as fact. No comedogenicity paper we read demonstrates a mechanism for this molecule; the assays counted comedones, they did not explain them. A mechanism asserted to dress up a rating is not evidence, and we have made that mistake elsewhere and corrected it. Human evidence: we identified no comedogenicity study that put isolated isopropyl palmitate on human skin and counted comedones. That absence is worth stating alongside what happened to its closest relative, which is the one ester in this cluster that has been tested on a human. Isopropyl myristate — the material of the definitional 5 — has been put on human skin, and there it looked far weaker than in the rabbit: the human test on record found it raised microcomedone counts from baseline but not significantly above occluded control skin — a null between-arm result — and a later clinical study declined to use it as a comedogenic positive control at all. That does not clear isopropyl palmitate — an untested material is untested, not exonerated, and unproven is not disproven — but it is the honest shape of the evidence: a high rabbit score whose human counterpart, for the sibling, deflated, and for this ester was never measured at all. The assay itself has been contested for decades, and here the objections cut toward the rabbit number as much as away from it. Frank asked in 1982 whether the rabbit ear predicts human acnegenicity at all. Draelos and DiNardo, in 2006, tested finished products on human backs and found that isolated ingredient scores did not transfer to the formulas they ended up in. A 2025 review in JAAD Reviews found that no standardised comedogenicity test exists and that the label "non-comedogenic" is unregulated. Those cautions apply to a positive grade exactly as much as to a reassuring one.

Where you’ll see it

On a label it appears as Isopropyl Palmitate. It is a common lightweight emollient in leave-on products where a dry, non-greasy slip is wanted — moisturisers, creams and lotions, cream and stick makeup, deodorants and antiperspirants, and cleansing and makeup-removal products — and it also turns up in hair care. We have not audited its market share, and label position is not a dose, so treat that list as the categories it suits rather than a measured prevalence. The Cosmetic Ingredient Review's safety assessment of the alkyl esters treats it as safe as used at the levels it reviewed; that is a safety judgement about toxicity and irritation, not a comedogenicity finding, and the two questions are separate. The practical point is the neighbour. "Isopropyl Palmitate" and "Isopropyl Myristate" are different esters that read almost identically on a label, and the comedogenic number people usually mean when they cite "the isopropyl myristate rating" is the one Fulton used to define his scale. This ester is the one beside it that was actually measured.

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 number in circulation, read off a render of the journal scan rather than a list quoting it. Method: 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 — three animals, a rabbit ear, not a human face. Its Table I prints isopropyl palmitate at a comedogenicity grade of 4 on a 0-to-5 scale, with no asterisk. Fulton's own key: 0 to 1 "not considered significant," 2 to 3 "borderline," 4 to 5 "considered positive." The same paper DEFINES grade 5 by isopropyl myristate — which also sits at 5 in the table — so the sibling's famous 5 is the scale's calibration point, a real but circular response rather than an independent reading. Fulton called his survey "not at all definitive but simply designed to stimulate research." acne.org, CosDNA and the rest republish this row; they are the same assay quoted, not independent corroboration.
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) An independent primary rabbit-ear assay on the same 0-to-5 scale, six years before Fulton and in a different laboratory — not a republisher of him. It scores isopropyl palmitate 3, applied undiluted. Cited as the one genuine second reading this page has: a different lab, testing the same named ester, also placed it in comedogenic territory. Its limit is the same as Fulton's — it is a rabbit ear, not a human face, and it tested the material neat rather than at an in-use concentration. Morris and Kwan are also on record contradicting Fulton on other materials, which is worth knowing: agreement here is not two labs that always agree.
3. Cosmetic Ingredient Review. "Amended Safety Assessment of Alkyl Esters as Used in Cosmetics." An expert-panel safety assessment covering isopropyl palmitate among the alkyl esters, cited for one narrow thing: it establishes that the ingredient is a widely used cosmetic emollient the panel judged safe as used at the concentrations it reviewed. A safety assessment weighs toxicity, irritation and sensitisation — not follicular plugging — so it is not evidence for or against a comedogenic rating, and we do not use it as one. Cited via CIR's stable ingredient record rather than a specific draft or tentative PDF.
4. Nguyen SH, Dang TP, Maibach HI. "Comedogenicity in rabbit: some cosmetic ingredients/vehicles." Cutan Ocul Toxicol 26(4):287-292 (2007) A third primary rabbit-ear assay, on a 0-to-4 scale — later than both Fulton and Morris and Kwan. Its abstract lists isopropyl palmitate among the materials deemed positive. Cited for that verdict only: we have NOT read its printed table, so we carry no numerical score from it and do not invent one. It matters because it is a third independent rabbit result pointing the same direction, which strengthens the rabbit evidence without adding a readable number.
5. 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: it is evidence that 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.
6. "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 reassuring ones and the alarming ones alike.

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 ›

• Butyl Stearate Clogging Low
• Caprylic/Capric Triglyceride Clear Low
• Cetyl Acetate Clogging Low
• Cetyl Palmitate Clear Low
• Decyl Oleate Clogging Low
• Isocetyl Stearate Caution Low
• Isopropyl Isostearate Clogging Low
• Isopropyl Linoleate Clogging Low

Last reviewed 2026-06-23 · How we decide

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