Sulfated Castor Oil
Sulfated castor oil — Turkey Red Oil — is a water-dispersible surfactant made by treating castor oil with sulfuric acid, and it is not the plain castor oil this site rates Clear. The only measurement we can find is Fulton's 1984 rabbit-ear table, which scored it 3 on a 0–5 scale, positive under that paper's own key; the larger 1989 table everyone quotes does not list it at all. We rate it Caution, on that single legacy reading.
Fulton 1984 printed 3 of 5 — positive under the 1984 key. It was tested after all.
What it is
On a label it is Sulfated Castor Oil, and older names for the same material are Turkey Red Oil and sulfonated castor oil (CAS 8002-33-3). It is made by reacting castor oil with sulfuric acid, which adds sulfate groups at the hydroxyl of the ricinoleic-acid chains and turns a thick, water-repelling triglyceride into a water-dispersible material — historically one of the first synthetic surfactants. Turkey Red Oil is a commercial reaction mixture rather than one invariant substance: the degree of sulfation, how far the product is neutralised and how much unreacted oil remains all vary between grades, and the CAS number covers that range rather than fixing it. Suppliers describe it as an amber-to-dark, water-soluble liquid used as an emulsifier, solubiliser and wetting agent: for dispersing essential oils into water, and in bath oils, liquid soaps and cleansers. The chemistry matters for one reason on this page. It is not the same substance as plain castor oil. Plain castor oil is the intact triglyceride; sulfated castor oil is that oil chemically altered into a surfactant. The two are rated separately here because the literature scored them separately, and conflating them is the most common way this ingredient's rating goes wrong.
Why we rate it Caution
We rate it Caution, at low confidence, on a single legacy rabbit-ear reading — and the reading is easy to attach to the wrong material, so it is worth being exact about what was measured. The measurement is Fulton, Pay and Fulton 1984 (J Am Acad Dermatol 10:96–105). Table I lists "Sulfated castor oil" at 3 on a 0–5 scale, applied "as is". The method is the rabbit-ear assay: the ingredient is applied to the inner ear of two New Zealand albino rabbits daily for two weeks, the opposite ear kept as control, and follicular keratosis graded 0–5, with borderline results confirmed microscopically. By this paper's own key, a grade of 1 to 2 is "not considered significant" and a grade of 3 or above is "considered positive" — so the 3 is a positive result under the key printed alongside its own table. Fulton's later 1989 survey uses a different key, and that key governs that paper's numbers, not this row. Two things this 3 is not. It is not plain castor oil's number — plain castor oil scores 1 in Fulton 1989, in his section VI, "Oils", whose heading carries the footnote "Results depend on source of raw material", and 0 to 1 in Morris and Kwan 1983, and it is rated Clear here. And it is not the "3" that the popular numeric charts print. Those charts descend from Fulton's 1989 table, and that table has no sulfated castor oil row at all; what it has is "Sulfated jojoba oil 3", a different material with an identical score. The one place the 3 belongs to sulfated castor oil is the 1984 paper — which those charts do not use.
What the evidence doesn’t tell you
This rests on one reading, from one laboratory, in one animal model, taken more than forty years ago, on two rabbits. Follicular keratosis in a rabbit's ear is not a comedone on a human face, and Fulton said as much about the sensitivity of his own assay. The ingredient was tested "as is", so there is no concentration series, and we hold no measured in-use concentration for it — the supplier literature describes the job it does, not the level it is used at. We identified no comedogenicity assay of sulfated castor oil outside Fulton 1984. Morris and Kwan 1983 tested plain castor oil, not the sulfated form; Nguyen, Dang and Maibach's 2007 rabbit-ear study names its fourteen test materials in its abstract, and this is not one of them. On the widely-copied numeric charts the material has no entry of its own; where it appears at all is the binary clinic "pore-clogging" avoid-lists, as Turkey Red Oil, with no method, no denominator and no citation behind it — an assertion, not a second measurement. We identified no human comedogenicity study of it. And the plain-oil literature does not transfer. Sulfation changes the material from an emollient triglyceride into a surfactant, so neither castor oil's low score nor its record on human skin tells you how the sulfated version behaves. The honest position is a single old rabbit reading of 3, and not much standing next to it.
Where you’ll see it
On a label as Sulfated Castor Oil, or under the older trade names Turkey Red Oil and sulfonated castor oil. Suppliers sell it as an emulsifier, solubiliser and wetting agent — for carrying essential oils into water, and in bath oils, liquid soaps, cleansers and some hair products — rather than as a leave-on facial oil. It also appears, as Turkey Red Oil, on the clinic pore-clogging avoid-lists that acne-prone shoppers use to screen products.
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.
- 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 primary source, and the only measurement of this exact material we can find. A rabbit-ear comedogenicity assay: two New Zealand albino rabbits per test, the agent applied to the inner ear daily for two weeks, follicular keratosis graded 0–5, borderline cases confirmed microscopically. Table I lists "Sulfated castor oil" at 3, used "as is" (undiluted). This paper's grade key differs from Fulton's better-known 1989 key: here 1–2 is "not considered significant" and 3 or above is "considered positive", so the 3 is positive under this paper's own key, and the 1989 bands are not applied to it. Read visually off a 400dpi render of the journal scan, because OCR drops the numeric column. A 1984 rabbit assay by one investigator group; not a human study, and we found no independent replication of it.
- Fulton JE. "Comedogenicity and irritancy of commonly used ingredients in skin care products." J Soc Cosmet Chem 40:321–333 (1989) Fulton's larger, later table, and the source of nearly every comedogenic number in circulation. Cited here for what it does NOT contain: there is no sulfated castor oil row anywhere in it. It lists "Sulfated jojoba oil 3" — a different, adjacent material — and plain "Castor oil 1" in section VI, "Oils", whose heading footnote reads "Results depend on source of raw material", both on the same 0–5 scale. Used here only to mark the material-identity boundary, not as evidence for this rating.
- Ataman Chemicals — Sulfated Castor Oil (Turkey Red Oil) technical description A supplier's technical/marketing monograph, not a comedogenicity source. Cited only for chemical identity and use: INCI Sulfated Castor Oil, CAS 8002-33-3, made by sulfonating castor oil with sulfuric acid to a water-soluble sulfate ester of ricinoleic acid, and sold as an emulsifier, solubiliser and wetting agent for essential oils, bath oils, liquid soaps and cleansers. Industry material describing what the substance is and does; it says nothing about pores.
- FWBEAUTY, "Comedogenic Ratings" (consumer chart, 2023) A representative example of the numeric "comedogenic ratings" charts that circulate online, all descended from Fulton 1989. Cited as evidence of the material-identity problem, not as a measurement: it lists "Sulfated Jojoba Oil – 3" and plain "Castor Oil – 1" and carries NO sulfated castor oil entry at all — so the chart most people would consult does not actually contain this ingredient. It cites no primary sources of its own and disclaims that its values were "compiled from various sources".
- Face Reality Skincare — Pore-Clogging Ingredient Checker A representative clinic-style binary "avoid" list, of the kind an acne-prone shopper uses to screen products. It names Turkey Red Oil / sulfated castor oil as an ingredient to avoid, with no number, no method, no patient count and no citation. Cited as an example of where a reader will actually meet the claim that this ingredient clogs pores — an assertion on a list, not evidence.
Others in the same family
Oils 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 oils as a family ›
Last reviewed 2026-08-12 · How we decide