Porecelain

Flawless skin starts with the fine print.

Palmitic Acid

Palmitic acid is one of the ingredients here whose circulating number actually belongs to it: Fulton's 1989 table prints a palmitic acid row and scores it 2 on a 0 to 5 scale — a figure its own author placed in his borderline band. This site's word for borderline is Caution, and that is the rating.

Caution Low confidence Legacy score 2 on a 0-5 scale · Fulton 1989 · low reliability

Fulton 1989 scored 2 of 5 — borderline under his own published key.

What it is

A saturated fatty acid, sixteen carbons long (C16), also called hexadecanoic acid, molecular weight 256.42. It is the most common saturated fatty acid in plants and animals, and it takes its name from palm oil, though it is abundant in most animal and vegetable fats. It is a waxy white solid at room temperature. In a formula it does the same mechanical work as its longer neighbour stearic acid: a thickener, co-emulsifier and opacifier that gives a cream or lotion its body, and when it meets an alkali in the pot — sodium or potassium hydroxide, or the amine triethanolamine — it may be partly or largely neutralised into a palmitate soap (sodium palmitate, potassium palmitate, TEA-palmitate), which is then a different material from the acid that went in. How much is neutralised depends on the formula, and we hold no measured figure for any particular product. Two points of identity matter before any number is quoted. First, "stearic acid" of commerce is grade-dependent, and many grades are mixtures of stearic and palmitic acids, so palmitic acid can be present, unlabelled, as a component of the stearic acid on an ingredient list. Second, and more often confused: palmitic acid is not any of the "palmitate" esters. Isopropyl palmitate and ethylhexyl palmitate each score 4 in the same Fulton table, and cetyl palmitate — a wax ester — scores 0. Sharing the word "palmitate" does not share a comedogenic number, and the ester carrying the highest of them is a different material from the acid on this page.

Why we rate it Caution

We rate it Caution, at Low confidence. The rating follows the paper's own key: Fulton graded palmitic acid 2 on his 0 to 5 scale, and he defined 2 to 3 as borderline. Borderline is what this site calls Caution. The confidence is low because the direct evidence is one rabbit-ear survey, a second-vehicle retest inside the same paper, and one older qualitative rabbit experiment we have read only in abstract — and nothing on a human face. On many pages of this site the circulating number turns out to belong to a different material, or to no measurement at all. Palmitic acid is not one of those. James Fulton's 1989 rabbit-ear survey in the Journal of the Society of Cosmetic Chemists prints a "Palmitic acid" row in the fatty-acid section of Table I and scores it 2 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. The number people quote for palmitic acid is a measurement of palmitic acid. The method behind it: the 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 then measured with a micrometer. And Fulton's own key to his own scale, which almost nobody quotes beside 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." By the standard of the man who produced it, a 2 sits at the bottom of the borderline band. It is above the range he called insignificant and well below his threshold for a positive result. It is not a finding of comedogenicity, and it is not a clean bill of health either. It is also worth noting which way this cuts against the consumer lists: several of them print palmitic acid at 0 to 1, lower than the figure Fulton actually recorded. The same paper prints the acid twice more. Fulton's Table III retested the fatty acids in other vehicles and records palmitic acid at 0 in an organic solvent — the table's footnote gives that as ethyl ether or acetone — and at 2 in sunflower oil. Two numbers under two conditions is what the table establishes. It is not a rule about vehicles, and we do not read one out of two cells. The neighbouring rows are worth printing as table content and not as a law. Fulton's fatty-acid run reads caprylic 1, capric 2, lauric 4, myristic 3, palmitic 2, stearic 2-3*, eicosanoic 2, behenic 0, where the asterisk is the paper's note that results depend on the source of the raw material. That is the shape of one man's column. We are not converting it into a chain-length rule about which acids clog: the paper's stated conclusion does not say that, and we will not supply one for it. The older rabbit experiment points away from a finding rather than towards one. Kanaar 1971, in Dermatologica, applied a series of fatty acids to the external ear canal of albino rabbits. Its abstract, which we read verbatim, reports that "myristinic, palmitinic and stearinic acid induced no distinct alterations". The Cosmetic Ingredient Review's fatty-acid report paraphrases the same experiment as producing transient erythema and scaling from palmitic acid. That paraphrase is a secondary reading and it is in tension with the abstract's own words, so we print both and lean on neither. The rest of the legacy record is empty on this material. Morris and Kwan's 1983 rabbit-ear survey prints no palmitic acid row. Fulton's earlier 1984 survey with Pay and Fulton prints none. The 2007 Nguyen, Dang and Maibach rabbit study did not test it. Isopropyl palmitate, which does appear in those tables, is an ester and a different material from the acid on this page. So the direct evidence is a borderline 2, a pair of vehicle readings of 0 and 2 in the same paper, and one qualitative negative read at abstract level. That is not a case for Clear. Fulton called 2 borderline, this site calls borderline Caution, and we are not arguing his own number down on mechanism, chain length or the fact that some of the acid is neutralised in the pot.

What the evidence doesn’t tell you

Two rabbit-ear experiments are still two rabbit-ear experiments. This is the same assay we discount everywhere else on this site, and the reasons do not stop applying because the result is undramatic. Draelos and DiNardo argued in 2006 that rabbit-ear results do not reliably predict comedogenicity in human skin; a 2025 review in JAAD Reviews 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. They apply identically to a borderline 2. We identified no study that counted comedones on human skin after applying palmitic acid. And the number is not a fixed property of the molecule: Fulton retested the fatty acids and reported the results in his own Table III, where palmitic acid graded 0 in an organic solvent and 2 in sunflower oil. Two cells under two conditions establish that the figure moves; they do not establish why. Kanaar 1971 we have read in part, and the part matters. We read the abstract verbatim, from EuropePMC, on 1 August 2026; we did not obtain the full paper. The method described here is as summarised in the Cosmetic Ingredient Review's fatty-acid report, and that report's account of the palmitic-acid result is a secondary reading in tension with the abstract's own words. We would rather say so than imply a closer reading than we have. Palmitic acid is not biologically inert, and it would be dishonest to leave that unsaid — but the evidence that it is active is not comedogenicity evidence, and it does not transfer to this rating in either direction. Palmitic acid is one of the most abundant free fatty acids in human sebum, and free fatty acids have long been implicated in the abnormal follicular keratinisation of acne; that is a description of the oil a follicle already produces, not a measurement of what a topically applied ingredient does to it. Separately, Jung and colleagues reported in Annals of Dermatology in 2021 that palmitic acid activated the NLRP3 inflammasome in cultured human sebocytes and, injected into mouse ear skin, produced inflammation. That study measured inflammasome activation and cytokine release from cultured cells and injected tissue — not comedone formation, not topical application, not a human face. It speaks to a possible inflammatory role in acne, which is a different question from whether the ingredient plugs a pore, and we do not read it as either supporting or overturning the comedogenic rating. We will not argue the rating from molecular size. The familiar online defence of the heavier fatty acids — that the molecule is simply too large to enter a follicle — is a mechanism we invented on a neighbouring page and had to retract, because the arithmetic did not support it. The rating rests on what the two assays found, not on a story about why they found it. Finally, the material identity is looser than a label suggests, and the salts are a separate question. Commercial palmitic acid and commercial stearic acid are both grade-dependent stearic/palmitic mixtures, so the "palmitic acid" in a jar and the "palmitic acid" on a rabbit's ear in 1989 were not necessarily identical. And the neutralised palmitate soaps a product actually contains — sodium, potassium and TEA-palmitate — are their own materials; the evidence on this page is for the plain acid and does not transfer to them.

Where you’ll see it

Creams, lotions, cleansing bars and milks, and lip and colour products, where it thickens and helps hold an emulsion together, often in company with stearic acid. On a label it reads simply as Palmitic Acid. Where it sits on that list is not a dose, and in a formula that neutralises it the material actually present may be a palmitate soap rather than the acid. These are illustrative categories, not a measured prevalence; we have not audited the market. Nearby you will meet the materials most easily confused with it, and the confusion is worth resolving because their numbers differ sharply. Its neighbours on the fatty-acid curve — lauric, myristic and stearic acid — carry different scores. Its own salts, the palmitate soaps, are separate materials. And the "palmitate" esters that share its name are not it at all: isopropyl palmitate and ethylhexyl palmitate score 4 in Fulton's table, cetyl palmitate scores 0, and none of them is the fatty acid rated here.

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 for the 0 to 5 scale nearly every list online still uses, read off a 400dpi render of the journal scan rather than via a chart quoting it. Design — 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. Its Table I prints "Palmitic acid" at 2, and its Table III records the same acid at 0 in an organic solvent and 2 in sunflower oil, so the figure moves with the vehicle. 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 such that 2 to 3 is borderline rather than positive. One animal assay, one laboratory, at roughly 10% in propylene glycol; we hold no measured in-use concentration for palmitic acid to set beside it.
  2. "Final Report on the Safety Assessment of Oleic Acid, Lauric Acid, Palmitic Acid, Myristic Acid, and Stearic Acid." J Am Coll Toxicol 6(3):321-401 (1987); with CIR's 2019 re-review, "Safety Assessment of Fatty Acids and Fatty Acid Salts as Used in Cosmetics" An industry-funded, independently panelled toxicological safety review — not a comedogenicity study, and palmitic acid is one of the five acids it is named for. Cited for two things we could read in it: its secondary summary of Kanaar 1971, which is where the transient-erythema description comes from and which does not match the Kanaar abstract, and the characterisation of palmitic acid as a commercial material (grade-dependent stearic/palmitic mixtures rather than the pure compound). Its overall conclusion is that these fatty acids are safe as used; safety is not noncomedogenicity, and the report counts no comedones.
  3. Kanaar P. "Follicular-keratogenic properties of fatty acids in the external ear canal of the rabbit." Dermatologica 142:14-22 (1971) The earliest primary rabbit-ear experiment on the fatty acids, eighteen years before Fulton, and genuinely independent of it. Provenance stated exactly: we read the abstract verbatim, from EuropePMC, on 1 August 2026, and did not obtain the full paper. The abstract reports that "myristinic, palmitinic and stearinic acid induced no distinct alterations". The method, and the description of palmitic acid as producing transient erythema and scaling, come at one remove from the CIR fatty-acid report above, and that paraphrase is in tension with the abstract.
  4. 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 second major rabbit-ear survey, on the same 0 to 5 scale, cited here for what it does NOT contain: its 32 rows cover lanolins, vegetable oils, esters and surfactants, and palmitic acid is not among them. It is a paper that could have corroborated or contradicted Fulton's figure and did neither. It matters for a second reason — it contradicts Fulton in print on other materials, so "one assay found 2" cannot be read as "the literature agrees".
  5. Jung Y-R, Shin J-M, Kim C-H, et al. "Activation of NLRP3 Inflammasome by Palmitic Acid in Human Sebocytes." Ann Dermatol 33(6):541-549 (2021) A mechanistic inflammation study, not a comedogenicity test. It found that palmitic acid activates the NLRP3 inflammasome in cultured human sebocytes — raising caspase-1 activity and IL-1β release via reactive oxygen species — and that palmitic acid injected intradermally into mouse ear skin produced visible inflammation at 24 hours. Its endpoints are cytokine and inflammasome activity in cultured cells and injected tissue; it counted no comedones, applied nothing topically, and did not study a human face. Included because palmitic acid is not biologically inert, but its relevance is to the inflammatory side of acne, not to whether the ingredient plugs a pore.
  6. 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 testing finished products on a small number of upper-back panels — not a same-substance rabbit-versus-human validation study. It argues that rabbit-ear results do not reliably predict comedogenicity in human skin and that testing an isolated ingredient says little about a finished formula. Cited against our own rating as much as for it: it is why the confidence here stays Low despite a low score.
  7. "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, and not independent of the legacy assays in the sense of testing anything — but independent of the consumer lists that republish them.

Others in the same family

Fatty acids 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 acids as a family ›

Last reviewed 2026-08-12 · How we decide

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