Porecelain

Flawless skin starts with the fine print.

Colloidal Sulfur

Colloidal sulfur is rated Caution, and the comedogenic 3 that trails it around the checkers is its own number. Fulton, Pay and Fulton's 1984 rabbit-ear table prints a row reading "Colloidal sulfur" and scores it 3, with no asterisk against it. That paper's own key reads 1 to 2 as not significant and 3 or above as considered positive, so by the standard of the study that produced it this is a positive result. The better-known 1989 survey is a separate paper with a separate key, and it has no colloidal sulfur row at all — which is where the idea that the 3 belonged to some other sulfur came from.

Caution Low confidence Legacy score 3 on a 0-5 scale · Fulton 1984 · low reliability

Fulton 1984 printed colloidal sulfur 3 of 5 — positive under the 1984 key.

What it is

Elemental sulfur — the yellow element, S8 — milled and dispersed so finely that it stays suspended, usually with the help of a protective colloid. On a label it is Sulfur or Colloidal Sulfur. It is an over-the-counter acne active in the United States: the FDA's monograph for acne drug products allows sulfur at 3 to 10%, and it also appears in treatments for rosacea, seborrhoeic dermatitis and dandruff. It works by keratolysis and has antimicrobial and anti-inflammatory activity. That is worth holding on to through the rest of this page, because it is half of an awkward pair. Colloidal sulfur is not a cosmetic emollient that strayed onto a bad-ingredients list; it is a drug used to treat the condition the list is warning about. It also carries a positive legacy comedogenicity row of its own. Both things are true at once, and that tension is the whole of the sulfur problem. The second thing is a distinction the checkers do not make and the papers do. Precipitated sulfur, sublimed sulfur ("flowers of sulfur") and colloidal sulfur are all the same substance — elemental sulfur — differing mainly in how finely divided the particles are, colloidal being the finest. "Water-soluble sulfur" is a different preparation again, a solubilised or complexed sulfur rather than the plain element. Those names matter here more than usual, because the legacy tables score them under separate rows, and in one table they score them differently.

Why we rate it Caution

We rate it Caution at Low confidence. Start with the number, because it is this material's own. What the 1984 table prints. Fulton, Pay and Fulton's rabbit-ear survey in the Journal of the American Academy of Dermatology carries a Table I row reading "Colloidal sulfur", scored 3, with no asterisk. That paper sets out its own key — "1 to 2 is not significant… 3 or above is considered positive" — so by the standard of the study that produced it, a 3 is a positive finding rather than a middling one. Whatever route the figure took to reach the checkers, it matches a real printed row for the exact material named on the label. Two things have to be held apart from that, because blurring them is what produced the confusion in the first place. The first is the other sulfur row in the same 1984 table: "Precipitated sulfur", asterisked, scored 0 to 2. In that paper the asterisk marks material diluted in mineral oil or made up as a 10% alcohol gel, and the table does not say which applied. So one paper scores two grades of the same element differently, under different preparations, and does not treat them as interchangeable. Neither will we. Precipitated sulfur's lower number is not available to lend to this page. The second is the 1989 paper, which is a different study with a different key and a different asterisk convention. Fulton's 1989 Table I, which we hold in verbatim transcription read off a 400dpi render, prints "Precipitated sulfur" at 0 and "Water-soluble sulfur" at 3, and it carries no colloidal sulfur row anywhere. That is a true and useful fact about the 1989 paper, and it is the origin of a reasonable-sounding story — that the 3 was lifted off the water-soluble row and pinned to the wrong name. The story does not survive the 1984 table, which prints the colloidal row and the 3 together. Note also that in 1989 the asterisk means "results depend on source of raw material", not dilution; the two conventions cannot be read across. There is older evidence, and it points the same way without adding a number. In 1972 Mills and Kligman, at the University of Pennsylvania, published "Is Sulphur Helpful or Harmful in Acne Vulgaris?" in the British Journal of Dermatology. Its summary reads: "Suspensions and creams containing elemental sulphur were shown to be capable of inducing comedones in the rabbit ear and on human backs. Sulphur compounds, sulphides, sulphites, thiosulphates and thiols were inactive in this respect. Even though sulphur was not strongly comedogenic, the thesis is presented that its daily application in the treatment of acne vulgaris might perpetuate rather than ameliorate the disease." We have read that abstract and nothing else of the paper, and the warnings in the limits section below are heavy ones. It is where the "sulfur paradox" comes from: a treatment that clears inflamed lesions while quietly seeding new comedones. So why Caution and not something stronger. Because a positive legacy row is still one reading, from one laboratory group, in a rabbit's ear, on a material the table names and does not otherwise characterise; and because the partly human corroboration is an abstract we have not been able to read behind. Caution is this site's word for a concern that is neither dismissible nor established. It is worth saying plainly what the rating is not: it is not advice against treating acne with sulfur, which is a clinical question this page does not answer.

What the evidence doesn’t tell you

The load-bearing number is one row in one table. Fulton, Pay and Fulton 1984 is a rabbit-ear study — two New Zealand albino rabbits per test, one ear dosed daily for two weeks with the other ear as the control, materials applied as they came unless marked with the dilution asterisk. The colloidal sulfur row is unasterisked, so it was not diluted in mineral oil or carried in a 10% alcohol gel; beyond that the table names the material and does not characterise it. Particle size is the whole difference between the elemental grades, and the paper does not record it, so what "colloidal sulfur" meant on that bench in 1984 cannot be recovered from the page. A rabbit's ear is not a face. Draelos and DiNardo's 2006 re-evaluation found that isolated rabbit-ear scores are a poor guide to how an ingredient behaves in a real formulation, and that objection applies to this 3 exactly as hard as it applies to anyone's 0. One positive row is also not a body of evidence agreeing with itself. The 1972 evidence needs its own warning, and it is a serious one. Mills and Kligman 1972 in the British Journal of Dermatology is not in our corpus. We have read its abstract from the publisher and no more, so its methods, sample sizes and grading are not in hand. It is also not the Kligman and Mills 1972 paper the rest of this site cites — that one is in Archives of Dermatology (106:843–850) and runs a 0 to 3 scale. Two papers, two journals, the same year, the same two authors in reversed order. We have kept them apart here and readers should too. The abstract we did read gives no comedogenicity score and no scale, so no number for sulfur can honestly be drawn from it, and we draw none. Its human arm was on backs, not faces, and half a century ago. The rest of the legacy corpus is silent on this material, and we checked rather than assumed. Fulton 1989 carries no colloidal sulfur row, as above. Morris and Kwan's 1983 rabbit-ear study does not include any sulfur among its thirty-two test materials. Nguyen, Dang and Maibach's 2007 assay does not include one either. Those are verified absences rather than zeros, and none of them subtracts from the 1984 row. We have also not verified from a primary document what Fulton's 1989 "water-soluble sulfur" was chemically, beyond that its name marks it as not the plain element; we report it as the row he printed. Concentration is unaddressed by all of this. The FDA acne monograph sets the active range at 3 to 10% sulfur, and we hold no measured in-use figure for colloidal sulfur in any particular product, nor any evidence about what a given concentration does on a human face.

Where you’ll see it

Almost always in things meant to treat, not moisturise: acne spot treatments, wash-off sulfur masks, medicated cleansers and sulfur soaps, and preparations for rosacea, seborrhoeic dermatitis and dandruff. In the United States the FDA acne monograph sets the active range at 3 to 10% sulfur. On a label look for Sulfur or Colloidal Sulfur. Two neighbours are worth keeping straight, because the legacy tables score them under their own rows. "Precipitated Sulfur" and "Flowers of Sulfur" (sublimed sulfur) are the same element as colloidal sulfur, differing in particle size. Precipitated sulfur has its own entries — 0 in the 1989 table, and 0 to 2 under a dilution asterisk in the 1984 one — and those numbers are its, not this page's. "Water-soluble sulfur" is a different preparation again, and the 3 it scores in the 1989 table is also not this page's 3. This page's 3 comes from the row that says colloidal.

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 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 for this page, and the paper that prints the row. Its Table I carries "Colloidal sulfur" scored 3, unasterisked, and separately "Precipitated sulfur" scored 0 to 2 with the asterisk that marks material diluted in mineral oil or made up as a 10% alcohol gel. Method: two New Zealand albino rabbits per test, one ear dosed daily for two weeks, the other ear the control. Its key is its own — "1 to 2 is not significant… 3 or above is considered positive" — and it is not the 1989 key, so numbers from the two papers cannot be pooled. Cited as the direct and exact evidence for this rating.
  2. Fulton JE. "Comedogenicity and irritancy of commonly used ingredients in skin care products." J Soc Cosmet Chem 40:321–333 (1989) The later and far more widely copied survey, read here from a 400dpi render of the journal scan rather than from a list quoting it. Method: ingredient at roughly 10% in propylene glycol, 1 ml applied to the inner ear of three New Zealand albino rabbits, five days a week for two weeks, follicular keratosis measured with a micrometer and graded 0–5, where 0–1 "is not considered significant". Cited for what it prints and what it does not: "Precipitated sulfur" at 0 and "Water-soluble sulfur" at 3, and no colloidal sulfur row anywhere in the table. Its asterisk means "results depend on source of raw material", which is not what the 1984 asterisk means.
  3. Mills OH, Kligman AM. "Is sulphur helpful or harmful in acne vulgaris?" Br J Dermatol 86(6):620–627 (1972). doi:10.1111/j.1365-2133.1972.tb05078.x Supporting evidence, held at arm's length. This paper is not in our corpus: we have read its abstract verbatim from the publisher (Oxford Academic) and no more, so method detail, sample sizes and any grading are not in hand. It is also a different paper from the Kligman and Mills 1972 study cited elsewhere on this site, which is in Archives of Dermatology (106:843–850) and uses a 0 to 3 scale; the two must not be merged. What the abstract establishes: suspensions and creams of elemental sulphur "were shown to be capable of inducing comedones in the rabbit ear and on human backs", while sulphur compounds (sulphides, sulphites, thiosulphates, thiols) "were inactive", and "sulphur was not strongly comedogenic". It reports no numeric score and no scale, so none is quoted from it here.
  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) An independent laboratory's rabbit-ear assay from a different group, whose thirty-two test materials were lanolins, vegetable oils, esters and surfactants. Cited for an absence: no sulfur of any grade is among them, so it neither corroborates nor contradicts the 1984 row.
  5. Nguyen SH, Dang TP, Maibach HI. "Comedogenicity in rabbit: some cosmetic ingredients/vehicles." Cutan Ocul Toxicol 26(4):287–292 (2007) A later rabbit ear-canal study on a 0–4 scale, a third scale and easy to misread as Fulton's. Its abstract names its test materials and no sulfur is among them. Cited for that absence.
  6. Sulfur — AHFS/drug monograph (topical sulfur; forms and dermatologic use) A drug monograph, cited only for what colloidal sulfur IS and how it is used, not for anything about pores. It is the basis for two statements on this page: that precipitated, sublimed ("flowers of sulfur") and colloidal sulfur are all elemental sulfur differing chiefly in particle size, precipitated and colloidal being the fine grades preferred for skin; and that topical sulfur is used as an acne, rosacea and seborrhoeic-dermatitis treatment. It says nothing about comedogenicity and is not used as if it did.
  7. acne.org comedogenic ingredient list A republisher of the legacy rabbit-ear scores, not an independent measurement. Cited as one of the places a reader meets the 3, and for the split it prints without explaining: "colloidal sulfur" at 3 and "flowers of sulfur" — the same element in a coarser grade — at 0. The 3 it prints matches the row Fulton, Pay and Fulton printed in 1984 for the exact material. We have not traced the chain from that table to this chart, and matching numbers are a strong hint rather than proof of copying.

Others in the same family

Actives 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 actives as a family ›

Last reviewed 2026-08-12 · How we decide

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