Sodium Lauryl Sulfate

Sodium lauryl sulfate carries a comedogenic 5 on most online lists, and — unlike most of the fives we chase down — that one does trace to a document: Fulton's 1984 rabbit assay, now read in full, scored it 5. But it is one of four disagreeing rabbit results. Fulton's own 1976 assay scored it 3 at 1% and 4 at 5%; Morris and Kwan 1983 scored it 0 at both 5% and 10%, saying in print that they conflict with Fulton; and Fulton's famous 1989 table has no sodium lauryl sulfate row at all.

What it is

An anionic surfactant: a twelve-carbon fatty chain with a sulfate group on the end. The Cosmetic Ingredient Review's 1983 safety assessment describes it and ammonium lauryl sulfate as detergents used in cosmetics as cleansing agents, and notes that sodium lauryl sulfate has "a degenerative effect on the cell membranes because of its protein denaturing properties." That is the mechanism behind both of the things it is known for: it lifts oil off skin and hair very effectively, and it strips lipid and denatures protein while doing it. It is the workhorse foaming detergent of shampoos, toothpastes and older facial cleansers, and it is also, in dermatology, the standard substance you use when you want to irritate skin on purpose — irritant patch testing uses it as a reference. On a label it is Sodium Lauryl Sulfate, sometimes Sodium Dodecyl Sulfate; SLS in shorthand. It is not sodium laureth sulfate, which is a different, ethoxylated molecule with its own entry, and which — as far as we can establish — no comedogenicity study has ever tested.

Why we rate it Caution

We rate it Caution, and the honest description of that rating is that the evidence is a disagreement, not a number. Start with what is not there. Fulton's 1989 rabbit-ear table is the source of nearly every comedogenic score in circulation, and it is unusually thorough about surfactants: it scores laureth-4 at 5, oleth-3 at 5, steareth-10 at 4, laureth-23 at 3, PEG 8 stearate at 3, sorbitan oleate at 3, ceteareth-20 at 2, and dozens more. Sodium lauryl sulfate is not in it. Not at 5, not at 0, not anywhere in the paper. The most-cited comedogenic list on the internet gives SLS a 5, and the table that list is quoting does not contain the ingredient. So where did the positive come from? An earlier version of this page said we could not establish it and left the matter there. That was wrong, and an external fact-check ran the trail down. It exists, and it is worth following, because the answer is more interesting than the shrug. The Cosmetic Ingredient Review's 1983 safety assessment of sodium and ammonium lauryl sulfate — an expert-panel review, not a comedogenic list — has a dedicated comedogenicity section, and it does not merely gesture. It describes the experiment: three albino rabbits, material applied to the internal base of the right pinna, Monday to Friday for two weeks, the left ear kept as a control, lesions scored on a 0–5 scale. And it gives the results. SLS at 1% scored 3. SLS at 5% scored 4. Its reference for that passage is Fulton JE, Bradley S, Agueda A, Black T, "Noncomedogenic cosmetics," Cutis 17:344 (1976) — an EARLIER Fulton paper than the famous one, whose own abstract independently confirms it found SLS comedogenic. And then the 5 itself, which for a long time this page called invented. That was wrong, and reading Fulton's OTHER paper is what corrected it. Fulton, Pay and Fulton 1984, in the Journal of the American Academy of Dermatology, prints a rabbit-ear table — now read in full, off the journal scan — and its row for sodium lauryl sulfate is a 5, used "as is." So the flat 5 the lists print is not invented after all; it is Fulton's own 1984 reading. What is still true is that it is one number among several that do not agree — 5 in 1984, 3-at-1%-and-4-at-5% in 1976, 0 in Morris and Kwan, no row at all in 1989 — and that Fulton's own results move with concentration, which a bare flat 5 destroys. We still have not read the 1976 Cutis paper; we are reading a careful regulatory summary of it. The 1984 table we have now read in its own document, so unlike the 1976 numbers its 5 is a score we have seen printed. It sits in ratings.yaml as a conflict, not a clean legacy number, because no single figure across these four results would be honest. Against them stands one exact-material assay we HAVE read. Morris and Kwan, in the Journal of the Society of Cosmetic Chemists in 1983, ran the rabbit-ear assay on 32 materials and scored sodium lauryl sulfate at 10% aqueous: 0. At 5% aqueous: 0. Ammonium lauryl sulfate at 10%: 0. They did not leave the contradiction implicit — they wrote it into the paper: "Our determination, and that of Kligman and Mills, of the noncomedogenic activity of sodium lauryl sulfate conflicts with the high scores published by Fulton et al." We used to say "the two rabbit studies we have read both scored it 0." We have read one. Morris and Kwan REPORT that Kligman and Mills also found SLS non-comedogenic, and we have not verified that in the original — the accessible 1972 abstract does not name SLS or give it a score. And Mills and Kligman's 1975 "Acne detergicans" is not a second SLS measurement at all: it tested finished soaps and shampoos at 25%, not the isolated surfactant. A finished shampoo is not an ingredient. So the score sheet, honestly: a 5 in Fulton 1984, read in its own table; a 3-at-1%-and-4-at-5% in Fulton 1976, read via a regulatory summary; one exact-material rabbit assay we have read finding 0 at both 5% and 10%, from investigators who said in print that they disagreed with Fulton; a second-hand report of another zero; and, in 1989, silence from Fulton himself, who kept sixty surfactants in his table and did not keep this one. That is not an invented number and it is not a missing one. It is a genuine, unresolved collision — three Fulton-family readings trending positive (3, 4, 5) against Morris and Kwan's flat 0 — and the internet flattened it into a single 5. The rating is Caution because the evidence conflicts, because SLS is rinsed off in seconds, and because no single number across these four results would be honest.

What the evidence doesn’t tell you

There is no human comedogenicity data on sodium lauryl sulfate. None. No cyanoacrylate follicular biopsy study, no facial trial, no comedone count on a person — for an ingredient that has been in daily contact with hundreds of millions of faces and scalps for seventy years. Every number ever attached to it comes from the inside of a rabbit's ear. This matters more here than on almost any other page, because of how SLS is used. The rabbit assay applies a material and leaves it there for weeks. SLS in the real world is a rinse-off surfactant: it is on skin for seconds, in a lather, and then it goes down the drain. CIR's conclusion turns on exactly this distinction — sodium and ammonium lauryl sulfate "appear to be safe in formulations designed for discontinuous, brief use followed by thorough rinsing from the surface of the skin," and "in products intended for prolonged contact with skin, concentrations should not exceed 1%." An occlusive rabbit-ear score of a leave-on application is not a measurement of what a cleanser does, and nobody we can find has run the study that would be. The comedogenic question is also, for this ingredient, probably the wrong question. SLS's large and genuinely independent human literature is about irritation, not pores. CIR reports it tested on human skin from 0.1% to 10%, with irritation increasing directly with concentration and open patches less irritating than closed ones. It is used in dermatology as a reference irritant precisely because that response is so reliable. Whether irritation and barrier disruption from a cleanser make acne worse in a given person is a reasonable thing to wonder and it is not a thing we can cite an answer to. We are not going to convert "it is a known irritant" into "it clogs pores," because those are different claims and only one of them has been measured. Two further cautions. The number circulating for SLS is often 5, on Fulton's 0–5 scale, where Fulton himself wrote that 4 to 5 is "uniformally reproduceable and considered positive" — a 5 is his top grade, the grade he gave isopropyl myristate, his standard positive control. That is an extraordinary claim about a rinse-off detergent — and it now has exactly one document behind it, Fulton 1984, against Morris and Kwan's zero and Fulton's own lower, concentration-dependent 1976 numbers. One positive reading at the top of the scale is not the same as a settled 5. And sodium laureth sulfate, the milder ethoxylated relative that has largely replaced SLS in cleansers, has no comedogenicity test we can find; scores you see for it are assertions, not measurements. Finally, the field-wide caveat. A 2025 review in JAAD Reviews, surveying the literature from 1972 onward, found that no standardised comedogenicity test exists and that the label "non-comedogenic" is unregulated. That applies to every page here. It applies with particular force to an ingredient whose famous score has no traceable paper under it.

Where you’ll see it

Foaming cleansers, shampoos, body washes, bar syndets, toothpastes and bubble baths — rinse-off products, almost without exception, and usually in the first five or six ingredients, because a detergent has to be present at percent-level concentrations to do anything. CIR's 1983 assessment discusses formulations from a fraction of a percent up to 30% detergent, with irritation rising across that range. In modern facial cleansers it has largely been displaced by sodium laureth sulfate and by amphoteric and non-ionic surfactants, which foam less harshly; where SLS survives, it is often in toothpaste and in cheaper shampoos. If you meet it in a leave-on product, that is unusual, and CIR's 1% ceiling for prolonged-contact formulations is the relevant number.

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. Cosmetic Ingredient Review Expert Panel. "Final Report on the Safety Assessment of Sodium Lauryl Sulfate and Ammonium Lauryl Sulfate." J Am Coll Toxicol 2(7):127–181 (1983) An independent expert-panel safety review, not a comedogenic list and not downstream of the comedogenic-rating industry. It is the single most useful document on this page. Its comedogenicity section does not merely assert a positive — it describes the whole experiment (three albino rabbits, internal base of the right pinna, Monday to Friday for two weeks, left ear as control, 0–5 scale) and gives the numbers: SLS at 1% scored 3, and at 5% scored 4. Its reference for the passage is Fulton, Bradley, Agueda & Black, "Noncomedogenic cosmetics," Cutis 17:344 (1976). An earlier version of this page said the attribution could not be established. It can. We have still not read the Cutis paper itself, so we are relying on a regulatory panel's careful account of it rather than the printed table — which is why those numbers are on the page and not in our legacy-score field. It also supplies the human irritation data (0.1%–10%, irritation rising with concentration, open patches milder than closed) and the conclusion the whole rinse-off question turns on: safe for "discontinuous, brief use followed by thorough rinsing," and not above 1% in products meant for prolonged contact. Read directly.
2. Fulton JE, Bradley S, Agueda A, Black T. "Noncomedogenic cosmetics." Cutis 17:344 (1976) The source of the positive, and a paper our own provenance map did not know existed — we had catalogued the legacy corpus as eight numeric documents, and this is a ninth. NOT READ: only the abstract, which confirms it found sodium lauryl sulfate comedogenic. Its actual scores (3 at 1%, 4 at 5%) reach us through CIR's 1983 account of it, above. Listed here so the trail is visible rather than implied, and flagged as second-hand so nobody — including us, later — mistakes it for a row we have read. Obtaining this paper is an open job.
3. 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) The source of the 5, and now READ in full off the journal scan (a print copy was obtained 2026-07-18) — this is the paper this page used to call "invented." Its Table I, under "Surfactants and detergents," prints "Sodium lauryl sulfate — 5," used "as is." So the flat 5 the charts print is Fulton's own 1984 reading, not a fabrication. Two caveats travel with it. First, its grade key is NOT the 1989 key: in 1984 Fulton wrote "1 to 2 is not significant… 3 or above is considered positive," so the threshold is set lower than 1989's. Second, it is one reading against Fulton's own 3/4 (1976, concentration-dependent) and Morris and Kwan's 0, so it settles that the 5 is real, not that it is right. A rabbit ear, two animals per test, two weeks — still not a human face.
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) A primary rabbit-ear assay, and one of the very few legacy papers that openly disagrees with Fulton and says so. Three rabbits, ear canal, 14 applications, microscopic grading, 0–5 scale. It scored sodium lauryl sulfate at 10% aqueous as 0, at 5% aqueous as 0, and ammonium lauryl sulfate at 10% aqueous as 0, and its discussion states: "Our determination, and that of Kligman and Mills, of the noncomedogenic activity of sodium lauryl sulfate conflicts with the high scores published by Fulton et al." Not an independent human study — it is still a rabbit's ear — but it is a primary measurement, not a republication, and it is the direct source of the number we would otherwise be guessing at.
5. Fulton JE. "Comedogenicity and irritancy of commonly used ingredients in skin care products." J Soc Cosmet Chem 40:321–333 (1989) The 220-row rabbit-ear table nearly every comedogenic score online descends from — cited here for what it does not contain. It scores laureth-4 at 5, oleth-3 at 5, steareth-10 at 4, laureth-23 at 3, PEG 200 dilaurate at 3, ceteareth-20 at 2 and dozens of other surfactants, and it has no sodium lauryl sulfate row. It also supplies Fulton's own grade key, which the lists quoting him leave out: a grade of 0 to 1 "is not considered significant," 2 to 3 is "borderline," and 4 to 5 is "uniformally reproduceable and considered positive." Method: roughly 10% in propylene glycol, applied to the inner ear of New Zealand albino rabbits, three rabbits per assay, follicles scored for keratosis.
6. Kligman AM, Mills OH. "Acne cosmetica." Arch Dermatol 106:843–850 (1972); and Mills OH, Kligman AM. "Acne detergicans." Arch Dermatol 111:65–68 (1975) Cited together, and cited with a warning: NEITHER IS A SECOND MEASUREMENT OF SLS, and we previously counted them as though they were. We have read them only through secondary description. The accessible 1972 abstract does not name sodium lauryl sulfate or give it a score — we know it found SLS non-comedogenic only because Morris and Kwan say so, in their paper, about someone else's. And 1975's "Acne detergicans" tested FINISHED SOAPS AND SHAMPOOS at 25%, not the isolated surfactant: 21 soaps and 18 shampoos, most non-comedogenic, many irritating. A finished shampoo is not an ingredient, and treating a product test as an ingredient test is the same category error we criticise everywhere else on this site. Note also that Kligman later repudiated the 1972 method for placing material in the protected ear canal with no untreated control ear — an objection that would make that assay OVER-call comedogenicity, not under-call it, which cuts against the reading that flatters SLS.
7. "Comedogenicity in cosmeceuticals: A review of clinical relevance, regulatory gaps, and future directions." JAAD Reviews (2025) Recent peer-reviewed review of the whole field, covering the 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. Finds that no standardised comedogenicity test exists and that "non-comedogenic" is an unregulated label. Cited for the field-wide caveat.
8. acne.org comedogenic ingredient list and its long-form companion article A republisher, and a comparatively careful one — it summarises the eleven legacy comedogenicity studies and lists its references, which is more than CosDNA, Face Reality, Banish or Sofie Pavitt do. It is still not an independent measurement, and the wider ecosystem of charts assigning sodium lauryl sulfate a flat 5 is one assay quoted many times over, not many sources agreeing. Cited here for two things we used it for: its account of what the 1972 and 1975 Kligman-and-Mills papers tested, and its own admission that comedogenicity testing is "normally performed by applying ingredients at 10% strength" while a finished product may contain far less — which is the whole problem with reading a rabbit-ear score as a fact about a cleanser.

Others in the same family

Surfactants behave similarly enough that the evidence for one is often wrongly read across to the others. These are its structural relatives, not a guess.

• Sodium Laureth Sulfate Caution Low

Last reviewed 2026-08-20 · How we decide

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