Laureth-4

Laureth-4 is one of the uncommon ingredients where the comedogenic number people cite is a genuine measurement of the exact material. Fulton's 1989 rabbit-ear assay scored it 5 on his 0–5 scale, the top of it, and his earlier 1984 paper scored it 4 on the same scale — both in the band each paper called positive. It is still one investigator and one model, in two small rabbit assays, and we identified no human comedogenicity study and no second laboratory.

What it is

Laureth-4 is a nonionic surfactant made by attaching a short chain of, on average, four ethylene-oxide units to lauryl alcohol — the twelve-carbon fatty alcohol that corresponds to lauric acid. On a label it is Laureth-4, and the "4" is that average number of ethylene-oxide units — an average, not a formula. The name describes a batch whose ethylene-oxide chains vary around four rather than a single tetraethoxylated molecule, and neither Fulton paper records the chain-length spread, the supplier or the grade of the material it tested. The EU CosIng database lists its functions as surfactant, emulsifying, antistatic and masking; the Cosmetic Ingredient Review's 2012 assessment of the alkyl PEG ethers describes it as a surfactant and emulsifier. In a formula it is usually the emulsifier that lets an oil disperse in water, which is why it turns up in shower oils, oil cleansers and cream makeup removers — the products that go on as an oil and rinse off as a milk. The CAS number usually printed against it, 5274-68-0, is tetraethylene glycol monododecyl ether — the tidy four-unit species, which is the idealised form of the name rather than a description of what is in the drum.

Why we rate it Clogging

We rate it Clogging, at Low confidence, and this page is unusual for one reason: the number is real. Most of the scores this site takes apart turn out to belong to a different material — a neighbouring row, a derivative, a dropped word. Laureth-4's does not. Fulton's 1989 table — the source of nearly every comedogenic number in circulation — prints Laureth-4 at 5 on his 0-to-5 scale. We read the row off the transcription of Table I rather than off a chart quoting it, and there is no ambiguity in it: the row is Laureth-4, not laureth-something-else, not a parent alcohol, not a blend, and it carries none of his qualifiers — no asterisk, no range, and it sits among the surfactants rather than in the oils section whose heading is asterisked. It matters what a 5 is in Fulton's own words, because the charts that publish his numbers leave his key out: "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." A 5 is the top of the scale — the grade Fulton anchored to isopropyl myristate, which he called "our standard 'positive' testing agent." So a 5 here means "produced follicular keratosis on the scale of isopropyl myristate in this assay." He also read it a second time. Fulton's earlier 1984 paper prints the row as Laureth-4*, at 4, carrying the paper's concentration asterisk: materials so marked "were either diluted with mineral oil or incorporated into an alcohol gel at a 10% concentration," and the table does not say which of the two was used here. That assay is also smaller and run differently — two New Zealand albino rabbits, the material applied to the inside of one ear daily for two weeks with the other ear as the control — where the 1989 survey used three rabbits and roughly 10% in propylene glycol. The two papers use different thresholds as well, so the numbers are not directly comparable, but they do not need to be: under the 1984 key ("a grading score of 3 or above is uniformly reproducible and considered positive"), a 4 is positive, and under the 1989 key a 5 is positive. Both of Fulton's readings land in the positive band. That is a genuine second reading, from the same investigator working the same model, and it points the same way. And Fulton named it in prose. His 1989 conclusion lists "the major offenders, such as isopropyl myristate, acetylated lanolin alcohol, and lauric acid derivatives such as laureth-4," and then closes the usual escape hatch: "We are not convinced of the statement that lower concentrations of these compounds can be safely used with no comedogenic consequences." That sentence is worth holding onto, because the standard defence of laureth-4 is that it only ever appears at low percentages — and the one author who measured it said, in print, that he did not accept that defence. One more thing his table shows, and only shows. Within his own laureth pair, the lightly ethoxylated Laureth-4 scored 5 while the far more heavily ethoxylated Laureth-23 scored 3; his oleth rows run the same direction (Oleth-3 a 5, Oleth-5 a 3, Oleth-10 a 2, Oleth-20 a 1). But the steareth rows in the same table do not: Steareth-2 is a 2, Steareth-10 a 4, Steareth-20 a 2, Steareth-100 a 0 — the middle of that series scores highest. And his prose on the lanolins runs the other way again, that "the classic anhydrous lanolins are not as comedogenic as the moderately ethoxylated derivatives." So this is a set of rows, not a law and not a mechanism, and it does not license reading laureth-4's 5 onto any other laureth. We report the rows and leave it there.

What the evidence doesn’t tell you

Everything above happened inside the ear of a rabbit: three of them in 1989, at roughly 10% in propylene glycol; two of them in 1984, with the material diluted in mineral oil or made up in an alcohol gel at 10%, and the paper does not record which. We identified no human comedogenicity study of laureth-4. Human data on the ingredient does exist, and it is worth saying what it is and is not — the CIR report records laureth-4 at 100% as "not an irritant" and "not a sensitizer" in human testing, and contains no comedogenicity testing at all. Irritation and sensitisation are different endpoints from a comedone count. A material can be neither an irritant nor a sensitiser and still plug a follicle, so those results neither support nor undercut the rating on this page. Both numbers are Fulton's own. This is where laureth-4 differs from an ingredient like castor oil, whose legacy score is confirmed by a second, independent laboratory. Morris and Kwan, whose 1983 assay ran on the same 0-to-5 scale and who were willing to contradict Fulton in print, did not test laureth-4 at all. So what the row survives is Fulton reading the material twice and naming it a third time — not confirmation by anyone else. We identified no non-Fulton measurement of laureth-4. The two readings are also not identical — 5, then 4 — and they were not taken the same way: different vehicles, different rabbit counts, and a dilution in 1984 the table does not fully specify. Two readings are not enough to say what moved the number, or whether anything did. But it is worth noting that the one flat value the charts print is not what the one investigator recorded. Fulton rejected the low-concentration defence, but rejecting it is not the same as measuring a threshold. He published no dose-response curve for laureth-4, and we identified no study establishing a percentage below which it stops producing comedones in the assay. "Not shown to be safe at low levels" and "shown to be unsafe at low levels" are different statements, and only the first is supported. Finally, the field-wide caveat that applies here as everywhere: the rabbit-ear model has been questioned since Frank's 1982 paper, and a 2025 review in JAAD Reviews, surveying the literature from 1972 on, found that no standardised comedogenicity test exists and that "non-comedogenic" is an unregulated label. Laureth-4's rating is well-supported by the standards of this subject. That remains a remark about the standards of this subject.

Where you’ll see it

On a label it is Laureth-4. The Cosmetic Ingredient Review's 2012 report on the alkyl PEG ethers records the family across bath, cleansing, hair and sunscreen products; in practice laureth-4 shows up most visibly in shower oils, oil cleansers and cream makeup removers, where its emulsifier function is what lets an applied oil rinse away with water, and it also appears in some foundations and sunscreens. Its ethoxylate relatives are separate entries here with their own scores, and — per Fulton's own table — not the same score: the more heavily ethoxylated members of the laureth and oleth series read lower than the lightly ethoxylated ones.

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 our legacy score and of nearly every comedogenic number in circulation. Method: the ingredient at roughly 10% in propylene glycol, applied to the inner ear of New Zealand albino rabbits, three rabbits per assay, five days a week for two weeks, follicles scored for keratosis on a 0–5 scale. Read off a transcription of Table I, not off a chart quoting it. It prints Laureth-4 at 5 — an exact row for this exact material, unasterisked and outside the oils section — alongside Laureth-23 at 3, the oleth series (Oleth-3 5, Oleth-5 3, Oleth-10 2, Oleth-20 1) and the steareth series, which does not run the same way (Steareth-2 2, Steareth-10 4, Steareth-20 2, Steareth-100 0). It supplies the grade key the charts omit — 0 to 1 not significant, 2 to 3 borderline, 4 to 5 positive — and, in its conclusion, names "lauric acid derivatives such as laureth-4" among "the major offenders" and rejects the claim that lower concentrations are safe. A rabbit-ear assay, and the author himself called the survey "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, on the same 0–5 scale but with a different threshold ("a minimal grade of 1 to 2 is not considered significant. However, a grading score of 3 or above is uniformly reproducible and considered positive"). Method: two New Zealand albino rabbits per test, the material applied to the inner surface of one ear daily for two weeks, the other ear as control — a smaller and differently run assay than 1989's. Its Table I prints Laureth-4* at 4, the asterisk marking materials that "were either diluted with mineral oil or incorporated into an alcohol gel at a 10% concentration"; the table does not say which applied here. Cited as the second reading of this exact material — same investigator, same model, five years apart, both readings positive under their own papers' keys — and as the reason the page can say the number was measured twice. It is not an independent laboratory, and it is still a rabbit's ear.
3. Fiume MM, Heldreth B, Bergfeld WF, et al. (Cosmetic Ingredient Review Expert Panel). "Safety Assessment of Alkyl PEG Ethers as Used in Cosmetics." Int J Toxicol 31(5 Suppl):169S–244S (2012) An independent expert-panel safety review of 369 alkyl PEG ethers, laureth-4 among them, and not a comedogenic assessment. This is the final published report, not a tentative or comment-stage draft. Cited only for what it actually establishes: that laureth-4 functions as a surfactant and emulsifier and is used in bath, cleansing, hair and sunscreen products; that in human testing laureth-4 at 100% was "not an irritant" and "not a sensitizer"; and that the Panel concluded the alkyl PEG ethers "are safe as used when formulated to be nonirritating." It contains no comedogenicity testing. It assesses safety, not comedogenicity — a different question — and says nothing about pores. (The panel also notes these ethoxylates can carry 1,4-dioxane as a manufacturing impurity; that is a purity-and-safety matter, not a comedogenicity one.)
4. Frank SB. "Is the rabbit ear model, in its present state, prophetic of acnegenicity?" J Am Acad Dermatol 6(3):373–377 (1982) The earliest peer-reviewed challenge to the assay both of this page's numbers come from. Cited for a caveat that cuts both ways: whatever weakens the model weakens a 5 exactly as much as it would weaken a 0. Not itself a comedogenicity measurement of anything.
5. "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, and independent of Fulton and of the charts that republish him. Finds that no standardised comedogenicity test exists and that "non-comedogenic" is an unregulated label. Cited for the field-wide caveat that sits under every legacy score on this site, laureth-4's included.

Others in the same family

Ethoxylates (PEGs & polysorbates) 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 ethoxylates (pegs & polysorbates) as a family ›

• Laureth-23 Caution Low
• Oleth-3 Clogging Low
• PEG-100 Stearate Clear Low
• PPG-5 Ceteth-10 Phosphate Clogging Low
• Steareth-10 Clogging Low

Last reviewed 2026-08-20 · How we decide

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