Porecelain

Flawless skin starts with the fine print.

Hydrocarbons

Four saturated hydrocarbons, all rated Clear, and the reason is unusual enough to be the page. This is the one family in the corpus we searched where the rabbit-ear assay was turned on its own verdict. Kligman and Mills condemned petrolatums and mineral oils as a class in 1972; in 1996 Kligman re-ran the assay on petrolatum, with a control the first version lacked, and called the earlier results false positives. Two findings come out of that paper and they are not the same finding - five refined petrolatums came out clean where a crude red veterinary petrolatum did not, which is about grade, and three tubs sold as Vaseline turned out to be unbranded greases of unknown composition, which is about what was in the tub. The withdrawal reaches two of our four members and no further.

4 rated 0 Clogging 0 Caution 4 Clear 1 never assayed

What they are

Saturated hydrocarbons. Carbon and hydrogen only - no ester bond, no glycerol backbone, no fatty acids. They are not fats, and that is why we file them apart from the oils rather than inside them. The four are mineral oil, a liquid petroleum distillate; petrolatum, the semisolid fraction of the same distillation; squalane, C30H62, which is squalene with all six of its double bonds hydrogenated away; and hydrogenated polyisobutene, a synthetic homopolymer of isobutene. THE FAMILY IS NOT "PETROLEUM PRODUCTS", and the difference does real work. Squalane is hydrogenated squalene, and squalene is a terpenoid recovered from plant and animal sources as well as from petroleum; hydrogenated polyisobutene is built up from a monomer. We hold no figures on how much of either is made from which feedstock and we are not going to guess at them. What holds the family together is the structure, not the origin, and any argument that runs on "petroleum" rather than on chemistry covers part of it at most. FULTON'S SECTION AND OUR FAMILY ARE DIFFERENT SETS. Three of our four appear in his 1989 Table I, and all three sit under one section heading - "VI. Oils*" - as Mineral oil, Squalane and Hydrogenated polyisobutane, spelled with an a. Petrolatum has no ingredient row in that table. So the 1989 ingredient table files three quarters of this family as oils and does not carry the fourth as an ingredient at all - which is a fact about that table rather than about the investigator, who did print an entry labelled Petrolatum in 1984, in the columns of his earlier table that list products. His sections are a formulator's categories, things that behave like an oil phase, rather than chemical ones, and where they diverge from our families is usually the interesting part. We mean OUR family unless we say otherwise; the member table below renders from our own ratings file. One further distinction, which we are going to keep separate rather than let bleed into the rest of the page. Refining grade is a documented variable for the two petroleum members - the International Agency for Research on Cancer classifies untreated and mildly-treated mineral oils separately from the highly-refined grades. That instrument is about carcinogenicity. It says nothing about pores in either direction and is not used here as though it did. It is cited for one narrow purpose - to show that "which grade" is a real question about these materials rather than a distinction this page invented.

What the evidence actually says

A great many of the materials on this site were scored once, by one paper, and never looked at again - not all of them, since Fulton read a number of rows twice across his 1984 and 1989 surveys and Morris and Kwan read others in a different laboratory. This family goes a step further. Two of these four were condemned as a class, and the condemnation was withdrawn by the man who made it, on the strength of experiments he re-ran on one of them. We identified no other family in the corpus we searched where that happened. THE ACCUSATION WAS MADE AT FAMILY LEVEL. In 1972 Kligman and Mills coined "acne cosmetica" in Archives of Dermatology, working the rabbit ear canal on a 0-to-3 scale, and reported that petrolatums and mineral oils from different sources were uniformly comedogenic. That is a sentence about a class of materials rather than about a table row, which is rare in this literature and is why the correction, when it came, was also family-sized. THE WITHDRAWAL WAS MADE AT FAMILY LEVEL TOO. In 1996, in the Journal of the Society of Cosmetic Chemists, Kligman wrote: "Using the original model, Kligman and Mills stated that petrolatums and mineral oils from different sources were uniformly comedogenic. With the updated model, it turns out that these were 'false positives'." He then names two defects in his own method. The material had been placed inside the ear canal, a protected site where loose horny squames are normally retained and mimic comedones. And the untreated opposite ear was never biopsied as a control, without which, he writes, "many materials will be falsely labeled as comedogenic". Be precise about what that is. There is no retraction notice and the 1972 paper stands as published; what he did was repudiate its positives for the bland greases and publish a corrected assay. "Retraction" has a specific publication-status meaning and this is not one. We have used the word loosely ourselves, on the mineral oil page, and it is the wrong word. What actually happened is narrower and more interesting than a retraction: he ran the experiment again, against himself, with the control the first version did not have. AND THE SAME PAPER CARRIES TWO FINDINGS, WHICH ARE WORTH KEEPING APART. The first is about grade. In the revised model, none of five petrolatum samples from different producers, white and yellow, was comedogenic. The assay had not simply gone blind - crude red veterinarian petrolatum, a wartime sunscreen, was strongly comedogenic in it, so the positives still came out positive. Five refined grades clean and one crude grade strongly positive is a result about refining, and it is the one this page is named for. The second finding is about identity, and it is a different kind of fact. Kligman bought "Vaseline" at six Philadelphia pharmacies; three turned out to be unbranded greases of unknown composition, and those three WERE comedogenic. What was in them is not recorded, so that is not a grade result at all - it is a result about how little the word on a tub tells you. Both belong on this page. Only the first of them is evidence that the score tracks the grade. FULTON PRINTED THE SAME FINDING IN A DIFFERENT NOTATION. His 1989 entry for mineral oil is not a number but a range, 0-2 on his 0-to-5 scale, and his prose says why: "Mineral oil presents a complex problem: some sources are acceptable; others are not." His own key reads 0-1 "is not considered significant", 2-3 "borderline" and 4-5 "considered positive", so that range starts below his threshold of significance and ends inside the borderline band. It was never a clean zero, and rounding it into one is what a chart does when it needs a single figure per row. AND THERE IS ONE MORE PRINTED ENTRY, WHICH THIS SITE HAS PREVIOUSLY WRITTEN AS THOUGH IT DID NOT EXIST. Fulton's earlier 1984 survey with Pay and Fulton carries, in the left-hand columns of its Table I, a Moisturizers group, and that group prints "Petrolatum - 0" and "Mineral oil - 0" alongside "Albolene - 0", on that paper's own 0-to-5 scale, whose key reads "a minimal grade of 1 to 2 is not considered significant. However, a grading score of 3 or above is uniformly reproducible and considered positive." Two caveats have to travel with those cells wherever they go. The first is that those left-hand columns list branded products and formulations rather than isolated ingredients, so an entry labelled Petrolatum there is a tub of something rather than a characterised material. The second is that our transcription of those columns is taken from a standard-resolution scan and has NOT been re-verified at 400dpi, unlike the ingredient rows we quote elsewhere. So this is not a legacy score for petrolatum and we are not going to give it one. What it is is the end of a sentence this site used to write, in which nothing anywhere had ever put a grade against that name. Something labelled petrolatum was graded, in 1984, at 0, in the part of the table where the identity of the material is least certain. So the family-level fact is this. For these materials the comedogenic result tracks the refining grade rather than the molecule, and this is the one place in the literature we have read where somebody tested two grades under the same name, in the same experiment, and got two different answers. Everywhere else source-dependence is a caveat in a footnote - Fulton's asterisk on "VI. Oils*", defined once as "Results depend on source of raw material". Here it is a result. NOW WHAT IT DOES NOT COVER, in the same breath rather than further down, because the sentence that tidies the argument is this page type's besetting fault. Neither squalane nor hydrogenated polyisobutene was named in the 1972 statement or included in the 1996 re-test. Each carries one graded row in Fulton's table - Squalane 1 of 5, and "Hydrogenated polyisobutane" 1 of 5, which our own page maps to hydrogenated polyisobutene as a judgement rather than a proof. For squalane that row is not the whole record, and the qualification belongs here rather than four paragraphs down - Motoyoshi's 1983 rabbit-ear experiment applied squalane and liquid paraffin and published a result for neither, and our squalane page cites it along with three papers on squalene peroxides. Both rows sit below Fulton's threshold of significance and both sit under the asterisked oils heading. Neither material is a refined petroleum fraction, so the grade finding does not transfer to them even in principle. Half this family rests on a correction. The other half rests on one graded reading each, and one of those readings is spelled differently from the ingredient it is quoted against.

What the evidence doesn’t tell you

THE HUMAN RECORD WE HAVE READ IS TWO SMALL NULL RESULTS, and a null in a small sample is weak evidence of absence rather than evidence of safety. It is not the whole human record on this family's materials, and the qualification goes here rather than nowhere - our own mineral oil page cites Mills and Kligman 1982, Arch Dermatol 118:903-905, which our legacy-assay notes record as a rabbit-ear AND human-back model with cyanoacrylate follicular biopsy on a 0-to-3 scale. We have not read it. Its abstract names no ingredient, we print no figure from it - a figure once published on this site against that paper was fabricated and retracted - and we cannot say from what we hold what it found for any material in this family. Of the two we have read: Kligman's 1996 study was twenty acne patients in two arms of ten, both arms receiving petrolatum, so there was no untreated arm and no vehicle comparator: it is a within-subject before-and-after null from one investigator in one city in one winter. Lee, Kim, Jung and Ha (2015) is eight acne-prone women, occluded upper-back skin rather than a face, and petrolatum was not the point of the study - microcomedone activity rose 55% under petrolatum and 54% at a site with no test material on it at all. Two small nulls are better than one. They are still two small nulls, and neither was powered to find a weak effect. AND HUMAN EVIDENCE IS NOT THIS FAMILY'S PROPERTY, which is the claim we most want to head off, including in ourselves. Coconut oil, which is an oil and is not in this family, has been applied to thirty whole human faces twice daily for a month, and we cite that study at length on its own page. The honest comparative statement is narrower - the human work we have read in this family is on one member, petrolatum, and the correction it belongs to was published by the same investigator who made the original accusation. At least one further human-model paper cited on our own mineral oil page, named above, we have not read. That is unusual. It is not unique, and it is not a claim about the whole literature. A NOT-POSITIVE IS NOT A ZERO. Nguyen, Dang and Maibach (2007) ran a rabbit assay on a 0-to-4 scale - a third scale, different again from Fulton's 0-to-5 and Kligman's 0-to-3 - and its abstract names both paraffin and petrolatum among the materials tested, reporting that the first nine of the fourteen were deemed positive. Those two are not among the nine. We have not read the full table, the abstract prints no per-material number, and we cannot tell whether their "paraffin" is liquid paraffin, which is mineral oil, or solid paraffin, which is a different material. We are reporting an ordering, not a score. ONE EXPERIMENT PUT TWO OF THESE ON SKIN AND WE CANNOT READ WHAT IT FOUND, which is why it is flagged up in the evidence above and not only here. Motoyoshi's 1983 rabbit-ear study tested six substances - squalene, oleic acid, tetradecane, isopropyl myristate, SQUALANE and LIQUID PARAFFIN, irradiated and not. The published abstract reports results for squalene and oleic acid and prints nothing for the other four. So a study that applied squalane and mineral oil to skin and counted comedones exists, we have not read the full text, and the gap cuts in both directions rather than in ours. THE COUNTER-SIGNAL IS REAL AND SHOULD NOT BE WAVED AWAY. Plewig, Fulton and Kligman described pomade acne in 1970 - closed comedones on the foreheads and temples of Black men using heavy hair pomades daily, with follicular plugging on biopsy - and Vaseline was named among the products implicated. The detail usually dropped is that the more elaborate formulations produced it more than the simpler preparations such as mineral oil and Vaseline did, which points away from the neat hydrocarbons rather than at them. An earlier report exists, Berlin (1954) on comedones in children under a paraffin-oil head preparation, and we have not been able to read it. We are listing it rather than writing as though it were not there. KNOWING THE SCORE BELONGS TO THE GRADE DOES NOT TELL YOU WHICH GRADE IS IN THE BOTTLE. "Mineral Oil", "Paraffinum Liquidum" and "Petrolatum" on an ingredient list identify an ingredient. They are not certificates of compliance with a pharmacopoeial monograph, and on the EU and US cosmetic declarations we have looked at, nothing obliges a manufacturer to say which grade is inside. That is the same practical limit the oil family runs into, arrived at from the other end: there the source dependence is asserted in a footnote, here it is demonstrated, and in neither case can a label tell you where in the range you are standing. THE INSTRUMENT IS THE ONE EVERYTHING ELSE HERE RUNS ON, AND IT IS NOT A GOOD ONE. Draelos and DiNardo (2006) tested finished products on small human upper-back panels and argued that an isolated ingredient's rabbit score says little about the product it ends up in; a 2025 review in JAAD Reviews, surveying the field from 1972 onward, finds that no standardised comedogenicity test exists and that "non-comedogenic" remains an unregulated label. Both objections apply to a reassuring 1 exactly as hard as to anyone's 4. FINALLY, THE SHAPE OF THIS PAGE IS ITSELF A REASON FOR SUSPICION. All four members are rated Clear, which makes a tidy family story unusually attractive to write, and a family-level generalisation is precisely the kind of claim this site exists to distrust - including, and especially, when we are the ones making it. What is established is one reversal covering two members. What is inferred is that it says anything at all about the other two, and we are not inferring it.

All 4 hydrocarbons 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. Kligman AM. "Petrolatum is not comedogenic in rabbits or humans: a critical reappraisal of the rabbit ear assay and the concept of 'acne cosmetica'." J Soc Cosmet Chem 47:41-48 (1996) The single most important document for this family, and read in full for this project's petrolatum page. It is two things at once. A human study - two groups of ten acne patients, refined petrolatum or a 30% petrolatum emulsion, twice daily to the whole face for eight weeks, with facial lesion counts and cyanoacrylate follicular biopsy of the forehead - in which neither comedones nor microcomedones increased. And a methods paper that re-runs the rabbit assay with untreated-ear controls, names the ear-canal site and the missing control biopsy as the source of the 1972 positives, and calls those results false positives. It is small, uncontrolled and by the same investigator who made the original accusation. It grades nothing on any numeric scale, so it cannot be the source of a legacy score, and it contains no lanolin experiment - a claim this project has had to retract elsewhere. There is no retraction notice attached to the 1972 paper.
  2. Kligman AM, Mills OH. "Acne cosmetica." Arch Dermatol 106:843-850 (1972) The original indictment, cited as the thing that was overturned rather than as support. Rabbit-ear-canal work on a 0-to-3 scale, a different scale from Fulton's, which reported that petrolatums and mineral oils from different sources were uniformly comedogenic. It is one of the few statements in the legacy corpus made about a class of materials rather than about a named row, which is why it can be reversed at family level. Its author later called its positives for the bland greases false positives; he did not retract the paper.
  3. Fulton JE. "Comedogenicity and irritancy of commonly used ingredients in skin care products." J Soc Cosmet Chem 40:321-333 (1989) The primary source behind nearly every comedogenic number in circulation, read off a render of the journal scan and transcribed by eye rather than quoted from a chart. Method: ingredient diluted to 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 under a micrometer. It carries three of our four members and it carries them inside section "VI. Oils*" - Mineral oil 0-2, Squalane 1, Hydrogenated polyisobutane 1, all on his 0-to-5 scale. It has no petrolatum ingredient row; the entry labelled Petrolatum is in the 1984 paper's product columns, not here. His asterisk is defined once, at the foot of the table, as "Results depend on source of raw material", and it sits on the section heading rather than on any cell. His own grade key reads 0-1 "not considered significant", 2-3 "borderline", 4-5 "considered positive". He described the survey as "not at all definitive but simply designed to stimulate research" and warned that the rabbit ear is sensitive enough that not everything which irritates it will irritate human skin.
  4. 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) Fulton's earlier rabbit-ear survey, and the only document we hold that prints a grade against the name Petrolatum. Its Table I runs in two parts - ingredient rows, and left-hand columns of branded products and formulations - and the Moisturizers group in those left-hand columns reads Albolene 0, Mineral oil 0 and Petrolatum 0. Its key is its own and is NOT the 1989 key - "a minimal grade of 1 to 2 is not considered significant. However, a grading score of 3 or above is uniformly reproducible and considered positive." What it cannot support - those left-hand columns list products and formulations rather than characterised ingredients, and our transcription of them comes from a standard-resolution scan and has not been re-verified at 400dpi as the ingredient rows were, so no legacy score for petrolatum may be built on them. It is also the same investigator as 1989, so agreement between the two is internal consistency rather than independent replication.
  5. Lee E, Kim N, Jung A, Ha J. "Isopropyl Myristate and Cocoa Butter are not Appropriate Positive Controls for Comedogenicity Assay in Asian Subjects." J Cosmetol Trichol 2:1000102 (2015) The independent human replication for petrolatum, from a different laboratory, continent and decade. Eight acne-prone women, petrolatum from Sigma, 0.3 mL over 16 square centimetres, three times weekly for four weeks under occlusion, microcomedones counted by cyanoacrylate follicular biopsy. Petrolatum rose 55%; a control site with no test material on it at all rose 54%. Part of its value is that petrolatum was not the point of the paper, which was asking whether the standard positive controls work in Asian skin. Eight subjects, upper back rather than face, and a null.
  6. Nguyen SH, Dang TP, Maibach HI. "Comedogenicity in rabbit: some cosmetic ingredients/vehicles." Cutan Ocul Toxicol 26(4):287-292 (2007) A later rabbit assay on a 0-to-4 scale - a third scale, easy to misread as Fulton's. We have read the abstract verbatim and not the full text. It names fourteen materials including paraffin and petrolatum and states that the first nine were deemed positive; those two fall outside the nine. It prints no per-material number anywhere we can see, so no number from it may be carried, and it does not say whether "paraffin" means liquid paraffin, which is mineral oil, or solid paraffin, which is not. Cited for an ordering and for that ambiguity, not for a score.
  7. Mills OH, Kligman AM. Arch Dermatol 118:903-905 (1982), carried here as our legacy-assay notes record the citation Listed because our own mineral oil page cites it and this page's human-evidence sentence would otherwise be written as though it did not exist. Our legacy-assay notes record it as a rabbit-ear AND human-back model, follicular hyperkeratosis read by cyanoacrylate biopsy, on a 0-to-3 scale. We have NOT read it - not the full text and not more than an abstract that names no ingredient - so we do not know what, if anything, it reports for any material in this family. No number from it appears on this page, and none may: a pair of figures this site once carried against this paper were fabricated and are retracted.
  8. Motoyoshi K. "Enhanced comedo formation in rabbit ear skin by squalene and oleic acid peroxides." Br J Dermatol 109(2):191-198 (1983) Cited for a gap rather than a finding, because the gap is ours to disclose. Its abstract lists the six substances applied to the ventral skin of rabbit ears - squalene, oleic acid, tetradecane, isopropyl myristate, squalane and liquid paraffin, irradiated and not - and reports outcomes for squalene and oleic acid only: squalene itself scarcely comedogenic, squalene peroxides highly so, with comedone size correlating with lipid peroxide level. Two members of this family were in that experiment. We have not read the full text and we do not claim to know what it found for either.
  9. Plewig G, Fulton JE, Kligman AM. "Pomade acne." Arch Dermatol 101:580-584 (1970) The human counter-signal, and more equivocal than either side of the argument usually admits. An observational report of closed comedones on the foreheads and temples of Black men using heavy hair pomades daily, with follicular plugging on biopsy, in which Vaseline is named among the products implicated. The pomades were mixtures and no component was isolated. Cited with the detail that is usually dropped: the more elaborate formulations produced pomade acne more than the simpler preparations such as mineral oil and Vaseline did.
  10. Draelos ZD, DiNardo JC. "A re-evaluation of the comedogenicity concept." J Am Acad Dermatol 54:507-512 (2006) A Current Issues and Opinion piece that tested FINISHED PRODUCTS on small human upper-back panels, six subjects per group for four weeks, and found products testing non-comedogenic despite containing ingredients the rabbit assay had scored. It is evidence that an isolated ingredient's score does not transfer to the formula it ends up in. It is NOT a same-material rabbit-versus-human validation, which is how it is usually cited, including previously by us, and it reports no per-ingredient number at all. Cited here against the reassuring readings on this page as much as for them.
  11. "Comedogenicity in cosmeceuticals: A review of clinical relevance, regulatory gaps, and future directions." JAAD Reviews (2025) A recent peer-reviewed review of the whole field, covering literature from 1972 onward, which finds that no standardised comedogenicity test exists and that "non-comedogenic" remains an unregulated label. It is a synthesis of the legacy corpus rather than a new measurement, and it is independent of Fulton only in authorship, since the literature it surveys includes his. Cited for the field-wide caveat, which applies to this family as much as to any other.
  12. IARC. "Mineral oils: untreated and mildly-treated oils (Group 1); highly-refined oils (Group 3)." IARC Monographs, Supplement 7 (1987) Cited for one narrow purpose and kept away from everything else. It is an evaluation of CARCINOGENICITY from occupational exposure, in which untreated and mildly-treated mineral oils are classified separately from the highly-refined grades used in cosmetics and pharmacy. It says nothing about pores in either direction and is not used here as though it did. Its relevance is that it establishes, in a formal instrument, that one ingredient name covers materials different enough to be assessed apart - which is the family-level point of this page, arrived at independently of any comedogenicity data. What we have read of it is the classification summary at the URL above, on the NCBI Bookshelf, and not the monograph volume itself. We hold no status line from the document and do not characterise the standing of the evaluation today.
  13. acne.org comedogenic ingredient list and its long-form companion article A republisher of the legacy assay scores rather than an independent measurement, and the same is true of CosDNA, Face Reality, Banish and Sofie Pavitt: matching numbers do not make five sources agreeing. We did not follow the citation chain and do not assert one. Listed for one fact about what the republishers say - acne.org's own long-form article states that petroleum jelly would qualify for its avoid list under its own rules and is excluded specifically because of Kligman's 1996 reappraisal, and mineral oil does not appear on the list either. That is a fact about the lists, not corroboration of anything.

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