Porecelain

Flawless skin starts with the fine print.

Humectants

All seven humectants on this site carry a comedogenic grade printed against their own name, and every one of those grades falls inside the band Fulton called insignificant. What no chart carries is where two of the seven sit in the machinery. Propylene glycol is the solvent the 1989 rabbit assay dissolved its test materials in, and glycerine is the negative control three human comedogenicity studies validated their method against - where its mean microcomedone grade came back 0.42, 0.76 and 0.82 on a 0-to-3 scale. This family supplies the reference conditions of both methods the subject rests on, and the human reference reading is not zero.

7 rated 0 Clogging 0 Caution 7 Clear 0 never assayed

What they are

Small water-soluble molecules that hold water. A humectant is hygroscopic - it draws moisture and keeps it in the upper layers of the skin - and a formulator reaches for one to stop a product drying out on the shelf or on the face. Seven members - glycerin, propylene glycol, butylene glycol, sorbitol, sodium PCA, sodium hyaluronate and panthenol. THE SEVEN ARE NOT ALL THE SAME KIND OF MOLECULE, and the differences matter to how they were tested. Four are small polyols - glycerin is a three-carbon triol, propylene glycol and butylene glycol are diols, sorbitol is a six-carbon sugar alcohol. Sodium PCA is the sodium salt of an amino acid derivative. Panthenol is an alcohol of pantothenic acid, and is in a formula at least as much for its soothing reputation as for water-binding. Sodium hyaluronate is not small at all - it is the sodium salt of a polysaccharide, orders of magnitude larger than the rest, and grouping it with glycerin is a decision about what an ingredient is FOR rather than what it is made of. "HUMECTANT" IS OUR FILING CATEGORY, NOT FULTON'S. His tables sort by function too, but into different bins, and our seven are scattered across his. In his 1989 table, propylene glycol and butylene glycol sit together at the head of a run of glycol esters; sorbitol sits above a run of sorbitan esters; glycerin sits above a run of glyceryl esters; and panthenol, sodium hyaluronate and sodium PCA appear singly, a long way down the table and a long way from each other. Our 400dpi transcription records section headings for only two blocks of that paper, so we describe those runs by their neighbouring rows and do not give them names the transcription does not hold. SEVERAL MATERIALS A READER WILL EXPECT HERE ARE NOT IN THIS FAMILY and will not appear in the table below. Propylene Glycol Monostearate, Glyceryl Stearate, Glyceryl Stearate SE, Polyglyceryl-3 Diisostearate, Sorbitan Oleate, Polysorbate 20 and Polysorbate 80 are fatty-acid esters of these humectants and we file them as EMULSIFIERS, in their own family, because that is what they are for. They share a root word with a humectant and carry their own, separate rows and their own, separate numbers - and on this site the sorbitol and glycerin pages each say so, because it is the single most likely way to misread a label in this family.

What the evidence actually says

Start with the seven rows, because they are short and because this is the rare family where the material identity holds all the way through. Fulton's 1989 survey, on his 0-to-5 scale, prints a row under each of these seven names. Propylene glycol 0. Butylene glycol 1. Sorbitol 0. Glycerin 0. Panthenol 0. Sodium hyaluronate 0. Sodium PCA 0. No asterisk on any of them, no range, no parenthetical, and no dropped word - each row names the material a label names. His earlier 1984 paper with Pay and Fulton reads two of the same seven again, on the same 0-to-5 scale - Glycerin 0, Propylene glycol 0 - and neither row carries that paper's dilution asterisk, which by its own footnote means the material "was used 'as is' if the agent was a liquid or soft solid". NOW THE KEY, once, for the whole family. Fulton 1989, p. 322 - "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." Every one of the nine readings above sits in the band he called insignificant. That is worth stating precisely rather than warmly - a grade in that band is the assay failing to register anything, which is not the same as the assay measuring nothing there. THE FAMILY-LEVEL FACT IS THAT TWO OF THESE SEVEN ARE NOT ONLY MATERIALS IN THIS LITERATURE. THEY ARE ITS REFERENCE CONDITIONS. That is the thing no single ingredient page can carry, because it is a statement about how the numbers on every other page were produced. THE RABBIT ASSAY'S CARRIER IS A MEMBER OF THIS FAMILY. Fulton's 1989 method diluted a test ingredient to roughly 10% in propylene glycol before applying it to the inner ear of three New Zealand albino rabbits. So the substance that delivered a great many of the numbers now in circulation has a row of its own in the same table, scored 0. He also printed one experiment on the carrier alone. Table II, on p. 331, grades a single colourant in four of them - "D&C red #36 in mineral oil" 3, "D&C red #35 in pentaerythrital tetra capra/caprylate" 2, "D&C #36 in propylene glycol" 1, "D&C red #36 in PEG 400" 0, all on the 0-to-5 scale, and we print those labels as they appear, #35 and the missing "red" included. One material, four carriers, three grades of spread. Our mineral hub reads that table for what it says about pigments; what it says here is narrower and more awkward - a member of this family is one of the four carriers, and it sits near the quiet end. What that does NOT establish is that propylene glycol is inert. It is one dye, it is one reading, and a carrier that keeps one colourant quiet is not thereby shown to keep anything else quiet. THE HUMAN ASSAY'S NEGATIVE CONTROL IS ALSO A MEMBER OF THIS FAMILY, AND ITS READING IS NOT ZERO. This is the part the charts have no way of showing. Three published human comedogenicity studies - 2021, 2025 and 2026 - run the same design: marked zones on the upper back of volunteers with prominent follicular orifices, a cyanoacrylate follicular biopsy taken before and after, repeated occluded patch applications across roughly a month, and microcomedones graded under light microscopy on a 0-to-3 scale where 0 is "non-comedogenic" and 3 is "large globoid microcomedones over the entire field". The 2021 and 2026 papers, which we read in full, both specify zones of about 3 by 3 cm and twelve applications on alternate days; we have read the 2025 paper's abstract rather than its full text, so we do not assert those details for it. In all three, coconut oil is the positive control and GLYCERINE IS THE NEGATIVE CONTROL. The glycerine readings, with their scale. Gala and colleagues, 2021, 22 of 24 participants analysed - mean comedone grade 0.82, SD 0.73, against coconut oil at 2.09, SD 0.68. Aich and colleagues, 2025, 26 analysed - glycerine 0.42, SD 0.76, coconut oil 1.92, SD 0.80. Gala and colleagues again, 2026, 29 analysed - glycerine 0.76, SD 0.58, coconut oil 2.07, SD 0.84. All on the same 0-to-3 scale. The 2026 paper is the one that prints the distribution behind its mean, and it is the most useful table in this family - of 29 people, 9 graded 0, 18 graded 1, 2 graded 2, and none graded 3. Twenty of twenty-nine had an endpoint grade above 0 under the material chosen to represent a clean result - and because the paper reports no baseline biopsy grade and no untreated occluded comparator, that is where those follicles finished, not a count of what the glycerine did. The papers are explicit about what glycerine is doing there. The 2026 study reports that "the method was validated by the significant difference (P = 0.001) between the positive and negative controls" - glycerine is the floor the method is checked against, not a material the study set out to learn anything about. And the reason it was chosen is a citation, not a measurement. That paper calls glycerine "a well-known humectant with non-comedogenic and non-occlusive properties, making it an ideal negative control", and the reference it hangs that on is a 2014 review of what moisturisers are made of, not a comedogenicity assay of glycerine. So the family's cleanest number and the discipline this site applies to numbers arrive at the same place. Glycerine reads low in human follicles, repeatedly, which is real evidence and better than most ingredients on this site will ever have. It also reads low BY DESIGN, and the low reading it produces is 0.42 to 0.82 on that 0-to-3 human scale rather than 0. That does not correct a rabbit 0 of 5, and we are not going to let it look as though it does - two methods, two species, two scales, and a reading from one of them cannot refute a reading from the other. What it establishes is narrower and is about the human method itself - its clean reference does not read 0 on its own scale, and none of the consumer charts we have looked at carries that number. AND THE THREE STUDIES ARE NOT THREE LABORATORIES. All three were funded by Dr. Reddy's Laboratories Ltd. and written by its employees, each testing a product in that company's own Venusia range. Monil Gala is corresponding author on the 2021 and 2026 papers and Snehal Muchhala co-authors all three, with Bhavesh Kotak on the two most recent. That does not make the control readings wrong - a negative control is the reading a sponsor has least reason to move - but three numbers from one programme is a consistency check, not a replication, and we would not accept it as three sources from anyone else.

What the evidence doesn’t tell you

THE FACT ABOVE REACHES TWO OF THE SEVEN. Sorbitol, sodium PCA, sodium hyaluronate, panthenol and butylene glycol are not the carrier of anything and have never been anybody's control. Each has one reading, in one paper, from one investigator - a single row in Fulton 1989 - and we identified no human comedogenicity reading of any of them, in the numeric documents we hold and in the searches run for their pages. Propylene glycol is the carrier and has two Fulton readings, but we identified no human comedogenicity study of the diol either. So the human evidence in this family is one member's, arriving sideways. WE CANNOT TELL YOU HOW MUCH OF GLYCERINE'S 0.76 IS GLYCERINE. None of the three studies, as we read them, reports an untreated site alongside the three treated ones, and none reports the baseline biopsy grade against which the final grade should be read. A month of occlusive patching is itself an intervention. The honest reading of 20 of 29 people grading above 0 under the negative control is that the floor of this method is above zero - not that glycerine put them there. Unproven is not disproven, and it is not proven either. NOR DO THE PAPERS SAY WHAT THE GLYCERINE WAS. No grade, no supplier, no purity, and no clear concentration - the 2026 paper describes applying "approximately 0.025 mL of the diluted test product and controls" without stating what the control was diluted to or with. That is the same gap we hold against Fulton, and it applies here. THE SECOND LABORATORY THAT COULD HAVE CHECKED THE LEGACY ROWS DID NOT TEST THEM. Morris and Kwan's 1983 rabbit-ear paper is an independent assay on the same 0-to-5 scale, from a different laboratory, and it contradicts Fulton in print on other materials. Its 32 rows contain no plain humectant. Propylene glycol appears in it twice and neither time as the article - once inside a material name, "Isopropyl Myristate (50% in Propylene Glycol)", where it is the vehicle again, and once as Propylene Glycol Isostearate, an ester scored 3-4, which is a different material and cannot corroborate or contradict the diol. Nor does the third rabbit-ear scale reach them - the fourteen materials named in Nguyen, Dang and Maibach's 2007 abstract include no member of this family, so the bounded absence above covers that paper too. A GRADE OF 0 IS NOT A MEASUREMENT OF SAFETY, AND WE ARE NOT GOING TO LET THIS FAMILY'S TIDY ROWS IMPLY OTHERWISE. Fulton called the 1989 survey "not at all definitive but simply designed to stimulate research", and warned that "not everything that irritates this model will also irritate human skin". Every objection this site raises against a rabbit-ear 4 applies to a rabbit-ear 0. Comedogenicity is also a narrow endpoint. Propylene glycol carries a substantial dermatology reputation that has nothing to do with pores, in contact allergy rather than in follicular plugging - a literature we have not read for this page and do not summarise here. Irritancy and allergy are different questions from follicular plugging, in both directions. A clean comedogenic row says nothing about them. AND FINALLY THE GENERALISATION ITSELF. Seven materials filed together because they hold water is our decision about a database, and a family-wide claim is exactly the kind of claim this site exists to distrust, including when we are the ones making it. The narrow sentence, and the only one we will defend, is this - two members of this family are the reference conditions of the two methods everything else here is measured by, and the human reference reading is not zero.

All 7 humectants 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 220-row rabbit-ear survey nearly every circulating comedogenic score descends from - 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 measured with a micrometer. Held here transcribed verbatim from a 400dpi render of the journal scan, because OCR drops the numeric columns. All seven members of this family have rows in it, on the 0-to-5 scale, none asterisked and none a range - propylene glycol 0, butylene glycol 1, sorbitol 0, glycerin 0, panthenol 0, sodium hyaluronate 0, sodium PCA 0. Also the source of the grade key on p. 322 and of Table II on p. 331, which grades one colourant at 3, 2, 1 and 0 across four carriers, one of which is propylene glycol. Fulton calls the whole survey "not at all definitive but simply designed to stimulate research". A single-investigator animal survey, not a clinical trial and not a human result.
  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). PMID 6229554 The earlier and far less quoted rabbit-ear paper from the same investigator, read off a 400dpi render of the journal scan - two New Zealand albino rabbits per test, one ear dosed daily for two weeks with the other as control, borderline cases confirmed by microscopic biopsy. It is the source of the second reading for glycerin and propylene glycol, both 0, and of the preparation note behind them - its asterisk marks materials "either diluted with mineral oil or incorporated into an alcohol gel at a 10% concentration", while an unmarked material "was used 'as is' if the agent was a liquid or soft solid". Its key is its own - 1 to 2 not significant, 3 or above positive - and is NOT the 1989 key. From the same programme as 1989, so concordance between the two is not independent replication.
  3. Gala MY, Muchhala SS, Charugulla SN, Rathod R, Mane A, Pandit S, Samal AR, Choudhury AA. "Evaluation of comedogenic potential of a paraben-free plant-based butter moisturizing cream - a double-blind, comparative study." CosmoDerma 1:52 (2021). doi 10.25259/CSDM_53_2021 A randomised, double-blind human comedogenicity study read in full text - 24 women with prominent follicular orifices on the upper back, 22 analysed, three marked zones, twelve occluded patch applications on alternate days, cyanoacrylate follicular biopsies before and after, microcomedones graded 0 to 3 under light microscopy. Cited for one thing only, and it is not the study's own conclusion - GLYCERINE WAS THE NEGATIVE CONTROL, at a mean comedone grade of 0.82, SD 0.73, against coconut oil as positive control at 2.09, SD 0.68. Funded by Dr. Reddy's Laboratories Ltd., all authors its employees, and the test product was the company's own moisturiser, which itself contains glycerin. It sets out to learn nothing about glycerine; the control reading is a by-product of validating the method.
  4. Aich B, Dhanaki GD, Sanghavi A, Muchhala S, Katare S, Kotak B. "Evaluation of comedogenic potential of a ceramide-based moisturizer (lotion/cream) - a prospective, randomized, double-blind, parallel-group comparative study." CosmoDerma 5:28 (2025) The second of the three, same design and same two controls - 30 female volunteers, 26 analysed, upper-back occluded patches, cyanoacrylate biopsies, microcomedones graded 0 to 3. GLYCERINE THE NEGATIVE CONTROL at a mean grade of 0.42, SD 0.76; coconut oil the positive control at 1.92, SD 0.80. Our glycerin page does not cite it - that page's source list holds Fulton 1989 and a consumer chart - so it appears here as one term in a series rather than as a reading the site already carried. Funded by Dr. Reddy's Laboratories Ltd., authored by its employees, testing that company's own moisturiser.
  5. Gala M, Muchhala S, Bhagat S, Sanghvi A, Kotak B. "A prospective, double-blinded, within-subject, site-randomized study to evaluate skin compatibility and non-comedogenic profile of Venusia acne facewash when applied topically under an occluded patch to the skin." CosmoDerma 6:24 (2026). doi 10.25259/CSDM_233_2025 The third, read in full text, and the only one of the three that prints the distribution behind its mean - which is why it carries most of this page. 30 subjects enrolled and 29 analysed, men and women, registered CTRI/2025/05/086182, same upper-back occluded-patch and cyanoacrylate design, same 0-to-3 grading. GLYCERINE THE NEGATIVE CONTROL at a mean grade of 0.76, SD 0.58 - and its per-subject table reads 9 subjects at grade 0, 18 at grade 1, 2 at grade 2, none at grade 3. Coconut oil the positive control at 2.07, SD 0.84. The paper states that "the method was validated by the significant difference (P = 0.001) between the positive and negative controls", and supports its choice of glycerine as non-comedogenic by citing a review of moisturiser constituents rather than an assay. It does not report the glycerine's grade, supplier or concentration, describing only "approximately 0.025 mL of the diluted test product and controls". Funded by Dr. Reddy's Laboratories Ltd., all authors its employees.
  6. Chularojanamontri L, Tuchinda P, Kulthanan K, Pongparit K. "Moisturizers for acne - what are their constituents?" J Clin Aesthet Dermatol 7:36-44 (2014) A REVIEW OF WHAT MOISTURISERS CONTAIN, cited for provenance alone. It is the document the 2026 study points to when it calls glycerine "a well-known humectant with non-comedogenic and non-occlusive properties, making it an ideal negative control". It is not a comedogenicity assay of glycerine and reports no comedone counts for it, so the choice of the reference material against which three human studies validated their method rests, at that link in the chain, on a review article. We have read the sentence citing it in the 2026 paper; we have not read the 2014 review in full.
  7. Nguyen SH, Dang TP, Maibach HI. "Comedogenicity in rabbit: some cosmetic ingredients/vehicles." Cutan Ocul Toxicol 26(4):287-292 (2007) The third rabbit-ear scale in this literature, 0 to 4, held as an abstract read verbatim rather than as a table. Cited for an absence - the fourteen materials its abstract names are esters, butters, alcohols, a surfactant and two hydrocarbons, and not one of this family's seven is among them. No per-material number appears in what we have read of it, and none may be carried from it, here or anywhere else.
  8. 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) The independent rabbit-ear assay on the same 0-to-5 scale, from a different laboratory, six years before Fulton's famous table - the document that would have corroborated or contradicted this family's legacy rows had it tested any of them. It did not. Its 32 rows are lanolins, vegetable oils, esters and surfactants, and contain no plain humectant. Propylene glycol appears in it only as a vehicle written into another material's name, "Isopropyl Myristate (50% in Propylene Glycol)", and as the separate ester Propylene Glycol Isostearate, scored 3-4. Cited for that absence, and because on other materials Morris and Kwan contradict Fulton in print and say so.

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