Myristic Acid

Myristic acid is rated Caution on a genuine Fulton score of 3 out of 5 — a real row for the free acid, not a borrowed one — but Fulton's own key calls 2–3 "borderline," the same paper prints 1 for it in a volatile solvent, an older rabbit study by a different laboratory found no distinct alterations from it at all, and what a finished cleanser puts on skin may be the myristate soap rather than the acid he tested.

What it is

A saturated fatty acid, fourteen carbons long — tetradecanoic acid, C14H28O2, molar mass roughly 228 g/mol, CAS 544-63-8, a white waxy solid. It sits between lauric acid (twelve carbons) and palmitic acid (sixteen) in the saturated series, and it takes its name from nutmeg, Myristica fragrans. The Cosmetic Ingredient Review describes the commercial material as made by the saponification and fractionation of animal or vegetable fats and oils. What a formula does with it matters for reading any number off it. Free myristic acid is a soap precursor: where a product also carries an alkali — sodium or potassium hydroxide, or triethanolamine — the acid and the alkali react in the pot, and what ends up on skin is partly or largely the corresponding myristate soap rather than the free acid. That is ordinary soap chemistry rather than a finding about pores, but it is not a distinction the literature glosses over: Fulton's own table prints "Stearic acid" and "Stearic acid: TEA" as two separate rows with two separate scores, so even the paper this page rests on treated a free fatty acid and its in-situ soap as different test materials. How much of either a given product contains depends on pH and stoichiometry, and an ingredient list does not tell you. The Cosmetic Ingredient Review's 2010 amended assessment of myristic acid and its salts and esters lists the acid's reported cosmetic functions as surfactant and cleansing agent, along with fragrance ingredient and opacifying agent, and concludes the group is safe as used. That is a safety finding, and it says nothing about pores. On a label it appears simply as Myristic Acid.

Why we rate it Caution

We rate it Caution, at Low confidence — Low because the only comedogenicity number we can find for it comes from a single rabbit-ear assay, which is the weakest tier of evidence this site records, and because the one other assay of the same acid we have found disagrees with it. The number is real, and it belongs to this material. Fulton's 1989 rabbit-ear survey in the Journal of the Society of Cosmetic Chemists — the largest of the legacy tables, at 220 rows — has a row for "Myristic acid," in its fatty-acids section, and it reads 3 on a 0–5 scale. That is worth saying plainly because it is the opposite of the usual finding on this site: no dropped word, no neighbouring ester standing in for the acid, no butter-for-oil substitution. Fulton tested free myristic acid and printed a number for free myristic acid. The match is to the free acid specifically, and that is where the caveat sits rather than at the name. A cleanser, shaving cream or soap bar listing Myristic Acid may present skin with sodium, potassium or triethanolamine myristate, or with a mixture of soap and unreacted acid, depending on how much alkali the formula carries. Fulton's 3 was measured on the free acid in his own vehicle. It is not automatically a number for the soap, and it is not a number for the myristate esters at all. What the 3 is worth is a separate question, and Fulton answered it himself. His published grade key, which almost no chart reproduces, reads: a grade of 0 to 1 "is not considered significant"; 2 to 3 is "borderline"; only 4 to 5 is "uniformally reproduceable and considered positive." A 3 is the top of the borderline band. It is not a clean pass, and it is not one of his positives either — it sits in the middle, where the assay itself is least sure. Caution is the word this site uses for exactly that. The charts that list myristic acid as a flat "3 — moderately comedogenic, avoid" are quoting the number and dropping the key that tells you what it meant. There is a second reading of the acid in the same paper, and it complicates the first rather than overturning it. Fulton's Table III set out to test whether the solvent an ingredient is dissolved in changes its score, and for the fatty acids it plainly does. That table prints myristic acid at 1 in an organic solvent — his footnote to the table specifies ethyl ether or acetone — and 3 in sunflower oil. This is not a second assay and not a second laboratory: it is a vehicle comparison inside the same research programme, published in the same paper, and it is not independent confirmation of anything. What it does establish is that the score moved with the vehicle. We cannot say from it which of the two readings a given finished product resembles, so the honest statement is that this ingredient's number is vehicle-dependent and a bare "3" hides that. A second laboratory read the same acid and found nothing distinct. Kanaar, in Dermatologica in 1971 — eighteen years before Fulton, and in the rabbit's external ear canal rather than on the inner surface of the ear — applied a series of free fatty acids and reported that lauric and oleic acid induced marked, and capric acid moderate, inflammation and follicular keratosis, while "myristinic, palmitinic and stearinic acid induced no distinct alterations." Myristinic acid is myristic acid: the same fourteen-carbon tetradecanoic acid under the older Latinate name. That is a direct disagreement with Fulton's 3, and it is not a number we can set against his. We have read the published abstract, not the paper, and while that abstract says the histologic changes were quantified and compared statistically in the paper's own Table I, we have not seen that table, so no scale, concentration, vehicle or animal count reaches us. What we hold is two rabbit assays, eighteen years and one method apart, reporting different things about the same material, and nothing that settles between them. That is why the rating stays at Caution and the confidence stays Low rather than either moving. One piece of context from Fulton's own numbers, offered as description and not as mechanism. Read down his saturated-fatty-acid rows and the scores rise and then fall: caprylic acid (eight carbons) 1, capric (ten) 2, lauric (twelve) 4, myristic (fourteen) 3, palmitic (sixteen) 2, stearic (eighteen) 2–3*, where the asterisk is Fulton's own footnote, "results depend on source of raw material." All are on his 0–5 scale. The peak is lauric acid, and myristic acid sits one step past it. That is what the table shows. The paper does not offer a mechanism for the shape, so we are not going to supply one, and a pattern across a table is not a prediction about salts, esters or other commercial grades. The point is only that myristic acid's 3 is not an isolated cell in his table.

What the evidence doesn’t tell you

The number above rests on one three-rabbit assay from one laboratory. Fulton's method was roughly 10% of the ingredient in propylene glycol, applied to the inner ear of New Zealand albino rabbits, three rabbits per assay, five days a week for two weeks, with the follicles then scored for keratosis under a micrometer. That is not a human face and it is not a finished product, and neither the concentration nor the vehicle need match the free-acid concentration or the chemical state of myristic acid in a cleanser. We are not going to turn that into a reassurance about dose: Fulton considered the argument and rejected it in the same paper, writing that "we are not convinced of the statement that lower concentrations of these compounds can be safely used with no comedogenic consequences." He also called his survey "not at all definitive but simply designed to stimulate research," and warned that the rabbit ear is sensitive enough that "not everything that irritates this model will also irritate human skin." The second reading of this acid is a contradiction rather than a confirmation, and that changes what the 3 is worth. Kanaar's 1971 ear-canal study reported no distinct alterations from myristic acid, so what we hold is not an unconfirmed 3 but a contradicted one. The two records cannot be placed on a common scale: Kanaar's result is a word rather than a score, from a different site in the ear, a different laboratory and a different decade, and we have his abstract rather than his paper. Where the two series can be compared at all, they agree at twelve carbons and part company above it — lauric acid is Fulton's highest straight-chain row at 4 on his 0–5 scale and Kanaar's "marked," while from fourteen carbons upwards Fulton printed 3, 2 and 2–3* for myristic, palmitic and stearic acid and Kanaar found nothing distinct from any of the three. Two laboratories disagreeing about one material is a different position from one laboratory being unconfirmed, and neither reading can be checked against the other. We identified no third reading. Fulton, Pay and Fulton's earlier 1984 rabbit-ear paper has no myristic acid row — its myristyl and myristate entries are all esters (isopropyl myristate 5, myristyl myristate 5, PPG-2 myristyl propionate 5, and myristyl lactate 5*, the asterisk being that paper's note that the material was diluted in mineral oil or run at 10% in an alcohol gel). Those are on a 0–5 scale too, but on that paper's own key, where 3 and above is positive rather than borderline, so they cannot be read against a 1989 number directly. Morris and Kwan's 1983 rabbit-ear paper, on the same 0–5 scale as Fulton 1989, likewise has no row for the acid; its myristate rows are the esters too, at 0–1 for myristyl myristate at 50% in mineral oil and 3–4 for isopropyl myristate at 50% in propylene glycol. We found no row for the acid in the other numeric legacy papers we hold. The consumer charts that print a 3 for myristic acid are reproducing Fulton's reading rather than adding one, and the one we cite does not mention Kanaar. We identified no human comedogenicity study of isolated myristic acid — no trial we could find has applied the acid alone, at a stated concentration, to human skin and counted comedones. The 2010 Cosmetic Ingredient Review report is a safety assessment, not a comedogenicity study. It concludes myristic acid and its salts and esters are safe as used and reports the acid as minimally or non-irritating in the dermal tests it collected, but irritation is not comedogenicity and a safety conclusion is not a measurement of pore-plugging. Where that report does discuss comedogenicity, it is discussing the esters — isopropyl myristate and myristyl myristate — and not the acid. It carries no comedogenic score for the acid, and we do not use it as one. Finally, the borderline band is genuinely uncertain in both directions. A 3 is not evidence that myristic acid is safe for acne-prone skin, and it is not evidence that it reliably clogs; it is the middle of a scale, from a method whose relevance to human skin has itself been questioned. Two papers bound how much a single borderline rabbit score can carry, though neither tested myristic acid: Draelos and DiNardo, building a human upper-back model in 2006, argued that a product made with a comedogenic ingredient is not necessarily comedogenic; and a 2025 review in JAAD Reviews found that no standardised comedogenicity test exists and that rabbit-ear results have been inconsistent in human skin.

Where you’ll see it

Most often in rinse-off cleansing products — facial washes, cleansing foams, shaving creams and soap bars — where it sits alongside an alkali and becomes the soap that produces a thick, creamy lather. The Cosmetic Ingredient Review lists its functions as surfactant and cleansing agent, fragrance ingredient and opacifying agent. Those are reported functions rather than a market survey we have conducted, and because it is commonly present as its soap rather than as the free acid, its position on an ingredient list tells you little about how much of either is there. It is worth keeping the acid separate from its relatives, since the myristate name travels widely and the numbers do not follow it. Isopropyl myristate and myristyl myristate are esters, not the free acid, and they have their own entries. Their legacy numbers are also not a single settled figure: Fulton 1989 prints both at 5 on his 0–5 scale, but grade 5 in that paper is defined as comedones "similar to those induced by the application of our standard 'positive' testing agent, isopropyl myristate" — so isopropyl myristate is the ruler rather than a reading — and Morris and Kwan scored myristyl myristate 0–1 at 50% in mineral oil on the same 0–5 scale. Sharing four letters with this ingredient is not evidence about it in either direction.

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, and the only document we hold that assigns free myristic acid a comedogenic number — Kanaar 1971 tested the same acid but reports no score we can read. Rabbit-ear assay: roughly 10% of the ingredient in propylene glycol, inner ear of three New Zealand albino rabbits, five days a week for two weeks, follicular keratosis scored under a micrometer. Read here off a 400dpi transcription of the printed table rather than off a list that quotes it. Table I, fatty-acids section, prints "Myristic acid — 3" on the 0–5 scale — a genuine row for the free acid, not a substitution. Table III, a vehicle comparison within the same paper rather than a separate experiment, prints myristic acid at 1 in an organic solvent (its footnote specifies ethyl ether or acetone) and 3 in sunflower oil. Fulton's own grade key: 0–1 "not considered significant," 2–3 "borderline," 4–5 "uniformally reproduceable and considered positive," so this 3 is the top of the borderline band and not one of his positives. He describes the survey as "not at all definitive."
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 paper, read in full from the printed table. Two New Zealand albino rabbits per test, one ear dosed daily for two weeks, the other ear the control. Cited here only for an absence and for the ester context: it has no row for free myristic acid, and its myristate entries are esters. Its grade key is not the 1989 key — 1 to 2 is not significant and 3 or above is positive — so a number from this paper cannot be read against a 1989 number without carrying each paper's own key.
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 primary rabbit-ear assay on the same 0–5 scale, published six years before Fulton 1989 and openly contradicting him in print on other materials. Rabbit ear canal, three rabbits, materials undiluted unless stated, 14 applications, microscopic grading. Thirty-two rows, none of them free myristic acid — it is cited here for that absence, and for its ester rows (myristyl myristate 0–1 at 50% in mineral oil; isopropyl myristate 3–4 at 50% in propylene glycol), which are a different material from the acid.
4. Kanaar P. "Follicular-keratogenic properties of fatty acids in the external ear canal of the rabbit." Dermatologica 142(1):14–22 (1971) The only document besides Fulton 1989 that we have found testing free myristic acid, and it disagrees with him. An independent rabbit assay eighteen years earlier, applying a series of free fatty acids in the external ear canal rather than to the inner surface of the ear, with the histologic changes quantified and compared statistically between treatment groups. Its reported result for this material is qualitative and negative — lauric and oleic acid marked, capric acid moderate inflammation and follicular keratosis, "myristinic, palmitinic and stearinic acid induced no distinct alterations," myristinic being the older name for myristic acid. We have read the published abstract only, from the publisher's own record for DOI 10.1159/000252365; PubMed indexes no abstract for it. The abstract says the changes were quantified in the paper's own Table I, but we have not seen that table, so no scale, concentration, vehicle or animal count reaches us and this result cannot be placed on Fulton's 0–5 scale or converted into one.
5. Becker LC, Bergfeld WF, Belsito DV, Hill RA, Klaassen CD, Marks JG, Shank RC, Slaga TJ, Snyder PW, Andersen FA (Cosmetic Ingredient Review). "Final Report of the Amended Safety Assessment of Myristic Acid and Its Salts and Esters as Used in Cosmetics." Int J Toxicol 29(4 Suppl):162S–186S (2010) An expert-panel safety review, not a comedogenic list and not downstream of Fulton. A final report, not a tentative or comment-stage draft. Cited only for what it establishes: myristic acid's reported cosmetic functions (surfactant and cleansing agent, fragrance ingredient, opacifying agent), its commercial production by saponification and fractionation of animal or vegetable fats and oils, and a conclusion that the acid and its salts and esters are safe as used, with the acid reported as minimally or non-irritating in dermal tests. It assesses safety and irritation, not comedogenicity, and the comedogenicity it does discuss is that of the esters. It carries no comedogenic score for the acid.
6. Draelos ZD, DiNardo JC. "A re-evaluation of the comedogenicity concept." J Am Acad Dermatol 54:507–512 (2006) A peer-reviewed "Current Issues" argument rather than a rabbit-versus-human validation, and it did not test myristic acid. The authors built a human upper-back occlusion model read by cyanoacrylate biopsy and concluded that a finished product made with a comedogenic ingredient is not necessarily comedogenic. Cited only for the limit it places on reading an ingredient-level rabbit number, and disclosed as opinion-piece framing rather than a controlled trial.
7. "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. It finds that no standardised comedogenicity test exists and that the rabbit-ear assay has produced inconsistent results in human skin. It makes no measurement of myristic acid; it is cited for the state of the method, not for a score.
8. National Center for Biotechnology Information. PubChem Compound Summary for CID 11005, Myristic Acid (tetradecanoic acid) A public chemical database entry, cited for chemical identity only: myristic acid is tetradecanoic acid, C14H28O2, molar mass ~228.37 g/mol, CAS 544-63-8, a fourteen-carbon saturated fatty acid. Not a comedogenicity source and not used as one.
9. acne.org comedogenic ingredient list A consumer chart that prints myristic acid at 3. The number matches Fulton's Table I row, which is where we take it to come from; it is a reproduction of that single reading rather than an independent measurement. Listed here because it is one of the places a reader will have met the number, and because its "3" is the same one, stripped of Fulton's borderline key.

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 ›

• Capric Acid Caution Low
• Lauric Acid Caution Low
• Palmitic Acid Caution Low
• Stearic Acid Caution Low

Last reviewed 2026-08-01 · How we decide

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