Carrageenan

We rate Carrageenan Caution at Low confidence — a precaution, not a measurement: it is a red-seaweed thickener that sits on acne-clinic avoid-lists, and the comedogenic number that trails it (trackers print 5, 4 and 3, and disagree with each other) traces to no assay we can find.

What it is

A seaweed thickener, and the red-algae counterpart to algin. The Cosmetic Ingredient Review's 2015 final report on polysaccharide gums defines it plainly: "Carrageenan is the plant material obtained from various members of the Gigartinaceae or Solieriaceae families of the red seaweed, Rhodophyceae," and, in the same document, "a high-molecular-weight sulfated polygalactan." Chemically it is a long carbohydrate chain — repeating galactose units carrying sulfate groups, which is roughly what the kappa, iota and lambda subtypes differ by (about one, two and three sulfate groups per disaccharide repeat, though the real subtype chemistry is more involved than that shorthand). It is far closer to a food gum than to anything on the fatty-acid or ester rows that most comedogenic scores come from; the same family of gel-formers is the food additive E407, and it thickens dairy, plant milks and toothpaste as readily as it thickens a cream. What it is doing in a formula is thickening it and giving it a gel-like body. CIR lists the cosmetic function of these gums as viscosity increasing, and reviews Carrageenan alongside its Calcium, Potassium and Sodium salts and a separate entry, Hydrolyzed Carrageenan. On a label it reads Carrageenan, or Sodium Carrageenan, or — because carrageenan is the principal polysaccharide of the red seaweed commonly called Irish moss — the related label name Chondrus Crispus Extract, which our checker maps here even though the whole-seaweed extract is not strictly identical to isolated carrageenan (see the limits below). It sits in the same seaweed cluster as algin (from brown algae) and algae extract, and the acne-clinic avoid-lists flag all three together.

Why we rate it Caution

We rate it Caution at Low confidence, on the evidence tier we call uncited-list — the same tier, and the same basis, as algin and algae extract. Start with the number, because the number is the reason anyone looks this ingredient up. Search "carrageenan comedogenic rating" and you will be told it is comedogenic and that acne-prone skin should avoid it — but you will not be told one number. Different trackers print 5, others 4, others 3, and a few call it low-risk. That spread is itself worth noticing: a single measurement would not normally surface as three different scores across three websites, and — as it turns out — none of these values traces to a study we can find. So we went looking for where any of these numbers comes from. We rendered Fulton's 1989 Table I and read all 220 rows by eye: there is no carrageenan row in it, no Chondrus row, and no red-algae, seaweed or kelp row of any kind. Morris and Kwan's 1983 assay — the other rabbit-ear study on the same 0 to 5 scale, six years earlier and in a different laboratory, whose 32 rows we hold in full — has no seaweed row either; its rows are lanolins, vegetable oils, esters and surfactants. And acne.org's compiled list of 45 comedogenic ingredients, drawn from eleven published rabbit-ear and human studies spanning 1968 to 2009, contains no algae-derived ingredient at all — not carrageenan, not algin, not kelp. This is not the coconut oil case, where the famous 4 belongs to coconut butter, or the lanolin case, where it belongs to the alcohol derivative. There is no neighbouring row to have misread. The number is attached to a material that no assay in the corpus we searched ever put on a bench. What actually stands behind the Caution is the thing that stands behind algin's and algae extract's: the pore-clogging avoid-lists that acne-focused estheticians keep. Face Reality's list, which our data cites, names Carrageenan alongside Chondrus Crispus, Algae Extract, Algin, Chlorella, Spirulina, Seaweed and Plankton. It is an alphabetical column of ingredient names on a brand's own site, published with no method, no scores, no patient counts and no reference to any study, next to products sold as free of the things on it. That is an opinion with a commercial interest attached, and we read it as one. The rationale usually offered for the whole seaweed cluster is iodine — that algae is iodine-rich, iodine is excreted through the follicle, and so it provokes comedones. We take that argument apart at length on the algae extract page and will not re-run it here; the short version is that iodine-induced eruptions are a neutrophilic hypersensitivity reaction rather than a plugged follicle, and the exposures that produce them are systemic doses of iodide, not a thickener in a cream. It applies even less cleanly to carrageenan than to whole kelp: carrageenan is a purified galactose-sulfate polysaccharide, and iodine is not part of its structure. Whatever iodine whole seaweed tissue carries, the isolated gum is not the vehicle for it. So why hold the Caution at all? Because practitioners who treat acne every day put this ingredient on a list, and we are not going to overrule people who see clogged skin merely because they did not publish. But an unpublished opinion is an opinion. We cannot tell you how many faces it rests on, because nobody who repeats it has said. The confidence is Low, the tier is literally called uncited-list, and that is the whole of what the rating is.

What the evidence doesn’t tell you

We can find no comedogenicity measurement of carrageenan, and we want to be exact about the shape of that absence rather than inflate it in either direction. What we checked: Fulton 1989 (no row), Morris and Kwan 1983 (no row), acne.org's 45-ingredient compilation of the published testing (no algae-derived ingredient), and the rest of the numeric corpus rendered at /how-we-decide, none of which assays it. That is the boundary of what we looked at. It is not a census of every proprietary, non-English or unpublished assay that might exist somewhere; a search is not a proof of a negative, and we are not going to dress one up as the other. Carrageenan does have a large safety literature — but it is about the gut, not the follicle, and it is easy to mistake one for the other. The European Food Safety Authority re-evaluated carrageenan (E 407) as a food additive in 2018, and the Cosmetic Ingredient Review assessed it as a cosmetic ingredient in 2015; both run to many pages. Neither is about pores. The EFSA work concerns ingestion, the distinction between food-grade carrageenan and "degraded carrageenan" (poligeenan), and effects on the intestine of animals fed it. The CIR report concerns skin and eye irritation, sensitisation and impurities; the words "comedogenic", "acne", "pore" and "follicle" do not appear anywhere in it. We cite these for what carrageenan is and where its real controversies live, and for nothing about comedones. Safety is not comedogenicity, and a controversy about the intestine is not evidence about a follicle. One caveat within that literature is worth stating precisely, because it cuts the other way. The CIR panel concluded that most of the polysaccharide gums it reviewed are safe as used, but that the available data were insufficient to conclude that Hydrolyzed Carrageenan — a separate, lower-molecular -weight ingredient made by breaking carrageenan down — is safe under the intended conditions of use. That is an open safety question about one derivative, recorded here so we do not leave the impression the whole family is settled. It is still not a comedogenicity finding, and it is not about the full-size gum that a formula usually contains. There is a smaller identity wrinkle than the one that dogs "algae extract", but it is not nothing. "Carrageenan" is a defined class of sulfated galactans, which is far tighter than the retired catch-all "algae extract" that can mean anything from a freshwater bacterium to a thirty-metre kelp. But the label synonym Chondrus Crispus Extract is not strictly identical to isolated carrageenan — it is the extract of one particular red seaweed, of which carrageenan is the main but not the only component — and the kappa, iota and lambda subtypes are chemically distinct. None of that manufactures evidence that was never collected. It only means the absence is about a reasonably well-defined material rather than a kingdom of them.

Where you’ll see it

As a thickener and gel-former: in gel creams, hydrating serums, sheet and peel-off masks, toothpastes, and "marine" or "blue beauty" moisturisers where red algae doubles as a positioning story. Those are illustrative categories, not a measured prevalence — we have not audited the market, and where it sits on a label tells you nothing about the dose. It appears as Carrageenan, Sodium Carrageenan or Chondrus Crispus Extract, with Calcium and Potassium Carrageenan and Hydrolyzed Carrageenan as relatives on the same kinds of products. It sits in the seaweed cluster with algin and algae extract. All three are on the same uncited avoid-list, and for all three we can find no assay — the number that trails each of them traces to nothing we could open.

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. "Safety Assessment of Polysaccharide Gums as Used in Cosmetics" — FINAL REPORT (October 22, 2015) A safety review of 106 polysaccharide gums, carrageenan and its salts among them, by the Cosmetic Ingredient Review — an industry-funded panel convened by the cosmetics trade association (the Personal Care Products Council) — read off the PDF whose cover reads "Status: Final Report. Release Date: October 22, 2015" — the final report, not one of the comment-stage CIR drafts this site has been burned by before. Source of the identity on this page: carrageenan is "the plant material obtained from various members of the Gigartinaceae or Solieriaceae families of the red seaweed, Rhodophyceae," "a high-molecular-weight sulfated polygalactan"; the panel reviews Calcium, Potassium and Sodium Carrageenan and a separate Hydrolyzed Carrageenan; the function of these gums is viscosity increasing. Also the source of the one open safety caveat: the panel found data insufficient to conclude Hydrolyzed Carrageenan is safe as used. It assesses safety, not comedogenicity — the words "comedogenic", "acne", "pore" and "follicle" do not appear in it — and we use it for nothing about pores.
2. 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 nearly every comedogenic number in circulation, and cited here for an ABSENCE. Read off a high-resolution render of the journal scan, all 220 rows of Table I transcribed by eye. It contains no carrageenan row, no Chondrus row, and no red-algae, seaweed or kelp row of any kind. Method: ingredient at roughly 10% in propylene glycol, inner ear of three New Zealand albino rabbits, five days a week for two weeks, follicular keratosis scored 0 to 5. There is nothing in it to attach a 5, a 4 or a 3 to.
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) An independent primary rabbit-ear assay on the same 0 to 5 scale, six years BEFORE Fulton 1989 and in a different laboratory — not a republisher of him, and it contradicts him in print on other materials. Cited here for what its 32 rows (seven lanolins, nine vegetable oils, eleven esters, five surfactants) do NOT contain: any seaweed or algae ingredient. The second of the two 0 to 5 assays we hold in full, and neither has ever scored carrageenan.
4. acne.org comedogenic ingredient list A compilation of 45 comedogenic ingredients drawn from eleven published rabbit-ear and human studies spanning 1968 to 2009 — the most complete catalogue of published comedogenicity testing that we hold. Cited here for the absence, which is the finding: it contains no algae-derived ingredient at all — not carrageenan, not algin, not kelp. A material that never appears in the catalogue of the testing was never in the testing. Not a republisher of Fulton alone; it states it synthesises multiple studies under a multi-study rule.
5. Face Reality Skincare pore-clogging ingredient list The entire basis of the Caution, and not a study. An uncited alphabetical list of ingredient names — Algae Extract, Algin, Carrageenan, Chondrus Crispus, Chlorella, Spirulina, Seaweed, Plankton among them — published on the site of a brand that sells products formulated without them. No method, no scores, no references, no patient counts. It tells you WHO flagged the ingredient. It does not tell you what they measured, and as far as anything public shows, the answer is nothing. This is the source the uncited-list evidence tier exists to describe honestly.
6. EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS). "Re-evaluation of carrageenan (E 407) and processed Eucheuma seaweed (E 407a) as food additives." EFSA Journal 16(4):5238 (2018) A large, current, final safety re-evaluation — cited to show where carrageenan's real controversies live, and that they are not comedogenic ones. It concerns INGESTION as a food additive: the distinction between food-grade carrageenan and degraded carrageenan (poligeenan), molecular-weight limits, and effects in the intestines of animals fed it. It measures no pores and is not about skin. Cited so that a reader who has heard "carrageenan is controversial" can see the controversy is a gastrointestinal one, on a different endpoint from anything this site rates.
7. Hesseler MJ et al. "An acneiform eruption secondary to iododerma." JAAD Case Reports 4(5):468–470 (2018). PMID 29984285 The primary document behind the iodine paragraph, cited only for the point that carries over from the algae extract and algin pages: iododerma most commonly presents as an acneiform eruption, but the biopsy shows a neutrophilic hypersensitivity reaction — an ulcer with neutrophils and fibrinoid necrosis — not a comedone, and the documented routes are systemic (iodinated contrast, potassium iodide, amiodarone) or iodine applied to broken skin as an antiseptic. It says the pathophysiology is unknown and gives no dose threshold. The wrong lesion, from the wrong kind of exposure — and carrageenan, a purified galactose-sulfate polysaccharide, does not carry iodine in the first place.

Others in the same family

Algae & seaweed 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 algae & seaweed as a family ›

• Algae Extract Caution Low
• Algin Caution Low

Last reviewed 2026-07-12 · How we decide

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