Porecelain

Flawless skin starts with the fine print.

Algae & seaweed

Algin, carrageenan and algae extract all carry comedogenic numbers on the trackers, and in the numeric documents we hold there is no seaweed row of any kind for those numbers to have been misread from. They trace to no primary document we could find, a condition they share with a dozen entries in our own untraceable block, rosehip oil and sodium chloride among them. What holds the cluster the avoid-lists flag together is provenance rather than chemistry — and algin and carrageenan are themselves defined materials.

3 rated 0 Clogging 3 Caution 0 Clear 3 never assayed

What they are

Three rated members, and they are not a chemical family. ALGIN is the sodium salt of alginic acid, which the Cosmetic Ingredient Review's 2015 final report on polysaccharide gums defines as "the carbohydrate obtained by the alkaline extraction of various species of brown seaweed, Phaeophyceae" — a linear polymer of mannuronic and guluronic acid, used to thicken. CARRAGEENAN is its red-seaweed counterpart, defined in the same report as "the plant material obtained from various members of the Gigartinaceae or Solieriaceae families of the red seaweed, Rhodophyceae" and as "a high-molecular-weight sulfated polygalactan" — also used to thicken. ALGAE EXTRACT is not a substance at all. It is an INCI label, published in 1979 and given retired status in 2015, which meant the extract of unspecified species of algae. A second proposition usually travels with that one, that the European Commission now requires the genus and the species in its place. It is a separate claim resting on a different document, and we have not read a Commission or CosIng entry that establishes it, so we record it as unverified rather than as fact. So two purified carbohydrates and a retired label. What holds them together is not chemistry, and we should say plainly that the axis is PROVENANCE — where the raw material was harvested. That is the same axis the acne-clinic avoid-lists use, and we have inherited it from them rather than arrived at it independently. The CIR's own brown-algae final report is blunter about the category than any critic could be: "algae" is not a taxonomic group, but a functional group of convenience. THE TABLE ON THIS PAGE HOLDS THREE INGREDIENTS AND ONLY THREE. A reader who has met this subject elsewhere will expect kelp, Chlorella, Spirulina, Laminaria, Chondrus Crispus, "Seaweed" and "Plankton" to be here too, because they sit together on the clinic lists. We do not rate any of them, so none of them appears below. Chondrus Crispus Extract is carried in our checker as an ALIAS that resolves to carrageenan, and calling it a synonym would overstate it: the mapping is a convenience with a known join in it, because the whole-seaweed extract is not strictly identical to the isolated gum, and the carrageenan page says so. One more piece of housekeeping, because it is the mistake this page is most likely to make. Fulton's table carries section headings, and HIS SECTIONS ARE NOT OUR FAMILIES. Our transcription records two of those headings and no more, so we cannot tell you what he called most of his blocks or which rows he filed under them. What we can tell you is that there is no algae row in his table at all. The materials that would sit nearest to algin and carrageenan chemically — the celluloses, the carbomer, chondroitin sulfate — are rows we file under other families entirely, and the section below says what they are worth.

What the evidence actually says

Three things, and the first two are the reason this family has a page rather than three pages that each say the same paragraph. FIRST, THERE IS NO ROW. We hold Fulton's 1989 Table I transcribed by eye off a 400dpi render of the journal scan, all 220 rows. It contains no algae row, no algin row, no alginate or alginic acid row, no carrageenan row, no Chondrus row, and no kelp, seaweed or Laminaria row. We hold Fulton, Pay and Fulton 1984 Table I the same way, read in full from a print copy: the same absence. Morris and Kwan's 1983 assay, an independent laboratory on the same 0 to 5 scale that contradicts Fulton in print on other materials, ran 32 rows — seven lanolins, nine vegetable oils, eleven esters, five surfactants — and no seaweed is among them. And acne.org's compilation of 45 comedogenic ingredients, drawn from eleven published rabbit-ear and human studies, contains no algae-derived ingredient at all. Nguyen and Maibach's 2007 rabbit-ear paper names fourteen test materials in its abstract, which is all of that paper we have read, and no seaweed-derived material is among them. That much each member page already says. Here is the part only a page above them can say. MANY of the misattributions recorded in our own retraction ledger and provenance file began as a real printed row read across to the wrong name. Coconut oil's famous 4 is coconut BUTTER at 4* of 5, the asterisk belonging to the section heading that row sits under and meaning that results depend on the source of the raw material. The 5 that circulates for wheat germ has no row of its own; what the paper prints is wheat germ GLYCERIDE at 3 of 5. Phenoxyethanol's 0 is phenoxyethyl PARABEN at 0 of 5. Salicylic acid's 0 is octyl SALICYLATE, a sunscreen ester, at 0 of 5. Ascorbic acid's number is ascorbyl PALMITATE at 2 of 5. Every one of those is a dropped word: a printed measurement of a real material, quietly attached to a neighbouring one. BUT NOT ALL OF THEM ARE, and our own ledger says so in terms. Its rosehip entry reads: "This is not even the usual failure of misreading an adjacent row. There is no row to misread. The number was attached to the paper by somebody who never opened it." Our provenance file records the same condition for sodium chloride, bakuchiol, argan oil, aloe, centella, niacinamide, azelaic acid, caprylyl glycol, sodium benzoate and lecithin. Algin, carrageenan and algae extract belong in that block rather than in a class of their own, and for all three there is no near-miss row we can point to either. The 4 that follows sodium alginate around, and the 5, 4 or 3 that different trackers print for carrageenan, are not measurements of the wrong material. They are not attached to a measurement we can find at all. SECOND, AND THIS IS WHAT MAKES THE ABSENCE MEAN SOMETHING: THE GAP IS NOT A CATEGORY FULTON DECLINED TO TEST. He put plenty of high-molecular-weight water-soluble thickeners on a rabbit's ear. In the nine rows that run together in the printed table immediately before his oils section, his 1989 table prints Carboxymethylcellulose at 0 of 5, Carboxypropylcellulose at 1 of 5, Hydroxypropylcellulose at 1 of 5, Magnesium aluminum silicate at 0 of 5, Carbomer 940 at 1 of 5, Bentonite at 0 of 5, Kaolin at 0 of 5, Talc at 1 of 5 and PVP at 0 of 5. Elsewhere in the same table he prints Sodium hyaluronate at 0 of 5 and Chondroitin sulfate at 0 of 5 — and chondroitin sulfate is a sulfated polysaccharide, which is the nearest structural neighbour carrageenan has anywhere in the document, and the one row here that a careless hand could plausibly have read across to it, though nothing in our ledger records that having happened. THOSE ARE HIS ROWS, NOT OURS. We rate none of them as algae; bentonite, kaolin and talc we file as minerals and sodium hyaluronate as a humectant, and the carbomer, the celluloses, the PVP and the chondroitin sulfate we do not rate at all. Nor do they give algin or carrageenan a score by proximity: promoting a neighbouring row into an empty one is the precise error this site exists to name, and it would be a poor page that committed it in the paragraph about not committing it. What the rows establish is narrower and it is the whole point. Gums, clays and polysaccharides were inside the survey's scope. The seaweed gums are missing from it anyway. THIRD, THE UNIT BEING FLAGGED IS THE ORGANISM, NOT THE MATERIAL. Face Reality's pore-clogging list, which is what our data actually cites for all three ratings, names Algae Extract, Algin, Carrageenan, Chondrus Crispus, Chlorella, Spirulina, Red Algae, Seaweed and Plankton. Those nine entries include a brown-algae uronic-acid polymer, a red-algae sulfated galactan, a green microalga, a cyanobacterium — Spirulina is a bacterium — a retired catch-all label, and two words, "Seaweed" and "Plankton", that name no cosmetic ingredient at all. They share no chemistry. They share a habitat. Almost every assay in the corpus we hold scores a NAMED MATERIAL at a stated concentration in a stated vehicle, and the exceptions do not help: Kanaar 1971 grades in words and carries no scale at all, and Fulton 1984's iron-oxides row is printed without the asterisk that would have recorded its carrier, so that vehicle is unresolved. Either way, a flag attached to an organism has nothing in that corpus it could ever have come from, and would not become one however many sites repeated it. The list itself is an alphabetical column of names on the site of a brand that sells products formulated without them: no method, no scores, no patient counts, no references. What that produces downstream is worth showing once, because it is checkable. On 25 August 2026 we read a page on AcneSafeCheck headed "Does Laminaria Digitata Extract clog pores?", which prints "a comedogenicity rating of 4/5 — high pore-clogging risk", says it is "Rated against the published comedogenicity references above", and lists as the first of those references Fulton, Pay and Fulton 1984 in J Am Acad Dermatol. We have read that paper's Table I in full. It has no Laminaria row and no algal row of any kind, and its grading key is not even the 1989 one — 1984 says "1 to 2 is not significant, 3 or above is considered positive", where 1989 says 0 to 1 is not significant, 2 to 3 is borderline and 4 to 5 is considered positive. That is one page, read on one day, and we are not characterising the site as a whole from it. Note also that Laminaria Digitata Extract is NOT one of the three ingredients we rate here — it is exactly the kind of species-level name that came into use in place of the retired "Algae Extract" label, which is to say a name the number could only have reached after 2015, decades after the tables it is credited to. The one mechanism ever offered for the whole cluster is iodine, and a hub is the place to answer it once. The argument runs that algae is iodine-rich, that iodine leaves through the follicle, and that this provokes comedones. It does not distribute evenly across these three even if you grant it: it is an argument about whole seaweed tissue, and algin and carrageenan are purified carbohydrates, with iodine forming no part of carrageenan's structure. It also fails on the lesion. Iododerma most often presents as an ACNEIFORM eruption in the areas of highest sebaceous density, which is the strongest form of the lists' case and we will not pretend otherwise; but the biopsy shows an ulcer with neutrophils, histiocytes and fibrinoid necrosis — a hypersensitivity reaction, not a plugged follicle — and the documented routes are systemic iodide or iodine applied to broken skin as an antiseptic. The CIR panel ran the exposure arithmetic itself and concluded that systemic iodine from the use of brown algae ingredients in cosmetics would be far less than that resulting from ingestion. And the 1961 paper the iodine idea is usually traced to, Hitch and Greenburg's questionnaire study of North Carolina adolescents, concluded that reasonable amounts of ingested iodine are not significant to the prevalence or severity of adolescent acne, and found the lowest acne rates among the teenagers eating the most seafood. The paper most often invoked for the mechanism argues against it.

What the evidence doesn’t tell you

None of the above says these ingredients are fine. An absent measurement is not a reassuring one, and the direction this page could most easily be misread in is the direction that suits a brand selling seaweed. All three keep a Caution, on the tier we call uncited-list, at Low confidence, because practitioners who treat acne every day put them on a list and we are not going to overrule people who see skin daily merely because they did not publish. An unpublished opinion is still an opinion, and we cannot tell you how many faces it rests on, because nobody who repeats it has said. The absence is bounded, and the boundary is the point. What we checked is the corpus rendered at /how-we-decide — nine numeric documents, of which the ones bearing on this family are Fulton 1989, Fulton 1984, Morris and Kwan 1983 and Nguyen and Maibach 2007 — plus acne.org's compilation, the CIR final reports on brown algae, red algae and polysaccharide gums, and the published human review below. That is a list of documents, not a census of the world's literature. Our own corpus file says to treat the corpus as OPEN, and it says so because a ninth numeric paper surfaced after we thought we had them all. If a proprietary, unpublished or non-English assay of a seaweed gum exists, our search would not have found it, and we are not going to dress a search up as a proof. We also went looking for the evidence that would complicate this page, and we should record what we found and could not finish. Murphy and Dow's 2021 systematic review of the human clinical literature on topical macroalgae identified eight human studies, all of moisturisation, pigmentation or cellulite; none measured comedones, and the word "comedogenic" does not appear in it. Separately, searches surfaced a body of work investigating seaweed-derived compounds AS acne treatments, including a trial of a formulation combining a brown-seaweed-derived oligosaccharide with zinc. We could not obtain those primary reports during this research — the databases hosting them served us a challenge page — so we carry no number, no finding and no citation from them. We record their existence only to say what we are therefore NOT claiming: not that the seaweed literature is empty, not that nothing marine has been put on a human face, and not that everything published about algae and acne runs the way the avoid-lists do. It plainly does not. Efficacy against acne and comedogenicity are different endpoints in any case, and a formulation containing zinc is not a test of an alga. The CIR reports are cited here for identity and for exposure, and for nothing about pores. The polysaccharide gums report assesses safety: the words "comedogenic", "acne", "pore" and "follicle" do not appear in it. The brown algae final report concludes that 68 of the 82 brown-algae INCI names it reviewed are safe as used, with insufficient data on the remaining 14 — a count of LABEL NAMES rather than distinct substances, several of which resolve to the same material — and it assesses no comedogenicity either. Safety is not comedogenicity. An unmeasured risk is not a measured safety. Both of those sentences have to hold at once on a page like this one, and the temptation is always to keep whichever one is convenient. Finally, the generalisation itself. A family-level claim is exactly the kind of claim this site exists to distrust, and that does not stop applying when we are the ones making it. The honest scope of the finding above is three ingredients, one clinic list, and the numeric documents that would most plausibly have held a seaweed row. It is not a statement about algae, about the ocean, or about what any given extract does in any given formula — and the deepest limit is the one the ratings cannot escape, that "algae extract" names a range of organisms rather than a molecule, so a single comedogenic verdict across it would be close to meaningless even if somebody had measured one.

All 3 algae & seaweed we rate

The legacy score is printed exactly as it appears in the paper, including the ranges, the asterisks and the parentheses. Those marks are not decoration. They are the paper telling you what its own number is worth.

Sources

  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 nearly every comedogenic number in circulation: ingredient at roughly 10% in propylene glycol, applied to the inner ear of three New Zealand albino rabbits, five days a week for two weeks, follicular keratosis graded 0 to 5. Read off a 400dpi render of the journal scan, all 220 rows of Table I transcribed by eye. Cited here for TWO things at once. For an absence: it contains no algae, algin, alginate, carrageenan, Chondrus, kelp, seaweed or Laminaria row. And for a presence, which is what makes the absence mean anything: it does contain the cellulose, carbomer, clay, PVP, sodium hyaluronate and chondroitin sulfate rows quoted on this page, so water-soluble thickeners and polysaccharides were within its scope. Fulton's own key — 0 to 1 not significant, 2 to 3 borderline, 4 to 5 considered positive — and his own description of the survey as "not at all definitive but simply designed to stimulate research" both apply to every number he printed.
  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) The earlier rabbit-ear paper, on its own 0 to 5 scale with a DIFFERENT KEY from the 1989 one: here 1 to 2 is not significant and 3 or above is considered positive, so a 1984 number may not be compared with a 1989 number without carrying each paper's key. It tested finished acne products and cosmetics as well as ingredients. Obtained as a print copy and transcribed at 400dpi rather than summarised from a list. Cited here because it contains no algal row of any kind, and because it is the reference a currently published comedogenic-rating page names for a 4/5 it prints against a seaweed extract.
  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. Undiluted material unless stated, 14 applications, microscopic grading. Cited for what its 32 rows do not contain: seven lanolins, nine vegetable oils, eleven esters and five surfactants, and no seaweed or algal ingredient among them. Its oils table is printed rotated and returns nothing to OCR, so anyone who scraped this paper by machine lost part of it; we hold a visual transcription.
  4. acne.org compilation of 45 comedogenic ingredients A republisher's compilation rather than a laboratory: a list of 45 ingredients said to be drawn from eleven published rabbit-ear and human studies. It is cited on this page for one absence and nothing else - no algae-derived ingredient appears in it. Because it reports other people's measurements it can corroborate nothing, and we carry no number from it; what it establishes is that a compilation assembled specifically to gather the comedogenic literature did not find a seaweed entry in it either.
  5. Face Reality Skincare pore-clogging ingredient list The entire basis of all three ratings in this family, and not a study. An uncited alphabetical column of ingredient names — Algae Extract, Algin, Carrageenan, Chondrus Crispus, Chlorella, Spirulina, Red Algae, Seaweed and 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, and no mechanism stated for any entry, which we mention because we have previously credited it with one it does not give. It tells you WHO flagged these ingredients. It does not tell you what was measured, and as far as anything public shows the answer is nothing. It is also the document that sets this family's boundary by organism rather than by material, which is the observation this page is built on. This is the source the uncited-list evidence tier exists to describe honestly.
  6. Cosmetic Ingredient Review. "Safety Assessment of Polysaccharide Gums as Used in Cosmetics" — FINAL REPORT (October 22, 2015) A safety review of 106 polysaccharide gums, algin and carrageenan among them, by an industry-funded panel convened by the Personal Care Products Council. Read off the PDF whose cover page reads "Status: Final Report. Release Date: October 22, 2015" — the final, not one of the comment-stage CIR drafts this site has been burned by before. Source of both identity definitions quoted on this page and of the viscosity-increasing function. 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.
  7. Cosmetic Ingredient Review. "Safety Assessment of Brown Algae-Derived Ingredients as Used in Cosmetics" — FINAL REPORT (October 2019) The final report, linked deliberately because this site once cited the March 2019 draft of it — a document stamped "Distributed for Comment Only — Do Not Cite or Quote" — and published a provisional count that the final reversed. Source of the statement that "algae" is not a taxonomic group but a functional group of convenience; of the 82 brown-algae INCI names and the conclusion that 68 of them are safe as used with insufficient data on 14; and of the finding that systemic iodine exposure from cosmetic algae would be far below dietary exposure. Comedogenicity is assessed nowhere in it, which is worth saying, because this is a document where a measurement would live if one existed.
  8. Hitch JM, Greenburg BG. "Adolescent acne and dietary iodine." Arch Dermatol 84:898–911 (1961) The paper the iodine-causes-acne idea is usually traced to, cited here because it does not support it: a dietary questionnaire study of North Carolina adolescents whose authors concluded that reasonable amounts of ingested iodine are not significant to the prevalence or severity of adolescent acne, and who observed the lowest acne rates among those eating the most fish and seafood. It is a study of diet, not of anything applied to skin. We can say this is where the idea is usually traced; we cannot say the clinic lists are tracing it, because the list we cite states no mechanism and cites nothing.
  9. Murphy MJ, Dow AA. "Clinical Studies of the Safety and Efficacy of Macroalgae Extracts in Cosmeceuticals." J Clin Aesthet Dermatol 14(10):37–41 (2021). PMID 34976289 A systematic review of the human clinical evidence for topical seaweed extracts, cited as the boundary of the human evidence rather than as reassurance. It identified eight human studies, all concerned with moisturisation, pigmentation or cellulite; none measured comedones and the word "comedogenic" does not appear in it. Its second author is the founder of an algae-based skincare company, which is exactly the kind of interest we insist on naming in the lists that flag algae, so we name it here.
  10. AcneSafeCheck. "Does Laminaria Digitata Extract Clog Pores? Comedogenic Rating 4/5" — page read 25 August 2026 Not evidence, and cited as an artefact rather than a source: one currently published page, fetched and read on one day, showing where a reader meets a number for a marine ingredient and what is offered as its provenance. It prints "a comedogenicity rating of 4/5 — high pore-clogging risk", states that its ratings are "Rated against the published comedogenicity references above", and lists Fulton, Pay and Fulton 1984 first among three references. We hold that paper's Table I in full and it has no Laminaria, kelp or algal row. Laminaria Digitata Extract is not an ingredient this site rates, and it is not in this family's table.

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