Petrolatum
Petrolatum has the strongest evidence behind it of anything we rate: two independent human studies, neither finding it comedogenic — and the first was run by the same dermatologist who had declared it comedogenic twenty-four years earlier, on his own patients, and published the reversal himself.
Once assumed comedogenic. Two independent human studies since have found nothing.
What it is
A semisolid mixture of hundreds of saturated hydrocarbons, produced by the fractional distillation of petroleum and then refined to remove colour, aromatic hydrocarbons and odorous material. Known generically as soft white paraffin; its specifications are set in the U.S. Pharmacopeia. It is not the same thing as mineral oil, which is the liquid fraction of the same family. Formulators reach for it as the reference occlusive — it sits on the surface, slows transepidermal water loss, and is used as an over-the-counter skin protectant. Kligman, reviewing its long clinical use for burns, abrasions, rashes and dry skin, notes that it does not merely sit inertly on top of the skin: it becomes incorporated into the intercellular lipid domains between corneocytes, becoming part of the structure of the horny layer.
Why we rate it Clear
We rate it Clear at High confidence. That word means something specific here, and less than it sounds. It does not mean the evidence is abundant. It means human beings were tested, twice, by different people, and neither test found anything. The first study is Albert Kligman's 1996 paper in the Journal of the Society of Cosmetic Chemists, titled, without much ceremony, "Petrolatum is not comedogenic in rabbits or humans." Two groups of ten acne patients — six men and four women in each, average age about eighteen, all with persistent moderate acne of at least two years and at least ten papulo-pustules and fifteen comedones at entry — applied a product twice daily to the entire face for eight weeks. One group used a highly refined petrolatum (Vaseline petroleum jelly); the other used an aqueous emulsion containing 30% petrolatum. Comedones and papulo-pustules were counted on the whole face at baseline and at eight weeks. Microcomedones were measured on the mid-forehead by cyanoacrylate follicular biopsy with image analysis — glue applied under a slide, lifted off with the outer horny layer and its vellus hairs attached, and the hairs encased in horny casts counted per square centimetre. Neither visible comedones nor microcomedone density increased. Both fell slightly, and neither fall was statistically significant. Papulo-pustules decreased significantly in both groups (p = 0.05, Student's t-test). No case worsened. The same paper reruns the rabbit assay and retracts the original finding. Kligman is the man who, with Otto Mills, coined "acne cosmetica" in 1972 and reported that petrolatums and mineral oils from different sources were uniformly comedogenic in the rabbit ear. In 1996 he names his own method's two errors — the 1972 test placed material inside the ear canal, a protected site where loose horny squames are normally retained and mimic comedones, and it failed to biopsy the untreated opposite ear as a control, without which "many materials will be falsely labeled as comedogenic." Re-tested with a revised protocol and proper controls, none of five petrolatum samples from different producers, white and yellow, was comedogenic. The revised assay was not simply blind to everything: crude "red veterinarian petrolatum," a World War II sunscreen, was strongly comedogenic in it. The positives still came out positive. The petrolatum did not. The second study is independent, and we had missed it. Lee, Kim, Jung and Ha (2015), working in Korea, applied petrolatum from Sigma to the upper backs of eight acne-prone women — 0.3 mL over 16 square centimetres, three times a week for four weeks, under occlusion — and counted microcomedones by cyanoacrylate follicular biopsy. Microcomedone activity rose 55%. At a control site with NO TEST MATERIAL ON IT AT ALL, it rose 54%. There was no significant difference between petrolatum and doing nothing. That is a different laboratory, a different continent, a different body site and a different decade from Kligman, and it lands in the same place. Now the correction, and it is ours. Our data used to carry a LEGACY SCORE of 0 for petrolatum, sourced to Kligman 1996 and marked verified. There is no such score. Kligman 1996 is a clinical study that reports lesion counts; it does not grade anything on a 0-to-5 or 0-to-3 scale. And Fulton's table — the source of nearly every legacy number in circulation — has no petrolatum row at all. We had taken a conclusion we agreed with, summarised it as a number, and put it in a field that means "a paper printed this." That is precisely what we accuse the comedogenic lists of doing, done by us, in the reassuring direction. The field is now blank, which is the honest value: an absence is not a zero. It is worth adding that acne.org, in its own accounting, says petroleum jelly would qualify for its avoid list under its own rules and is excluded specifically because of the 1996 reappraisal — so even the lists know.
What the evidence doesn’t tell you
Twenty people. Ten per arm, one investigator, one district of South Philadelphia, one winter. Both arms received petrolatum, so there was no untreated arm and no vehicle comparator: the finding of no comedogenicity is a within-subject before-and-after null, not a controlled contrast. A null result in ten people is weak evidence of absence, and the study was not designed or powered to detect a small comedogenic effect. The indictment and the exoneration come from the same laboratory, and several of the supporting claims in the paper's discussion are marked "unpublished observations." The second study helps, and it helps less than it looks. Lee's eight subjects are eight, its exposure was occluded upper-back skin rather than a face, and its purpose was not to test petrolatum at all — petrolatum was one material among several in a study asking whether the standard positive controls work in Asian subjects. Two small null results are better than one small null result. They are still two small null results, and neither was powered to find a weak effect. High confidence, in our system, means human beings were tested. It does not mean the question is closed, and we would rather tell you what High is worth than let the word do work it has not earned. The significant result — fewer papulo-pustules — is not evidence that petrolatum treats acne, and Kligman says so in the paper: "This study is not intended as a recommendation of petrolatum for the treatment of inflammatory acne vulgaris." He notes that in vehicle-controlled acne trials the vehicle alone routinely produces a benefit approaching that of the active drug. Acne improves under observation. That is a known artefact, and it is the honest reading of that number. Grade is load-bearing, and the label does not tell you the grade. This is the caveat we most want you to leave with. What was tested was refined, pharmacopoeial-grade petrolatum — and we previously wrote that this "is what a cosmetic ingredient list means by the word." It is not. The INCI name "Petrolatum" on a package certifies nothing about refinement: USP and Ph. Eur. monographs exist, but an ingredient list is not a certificate of compliance with one, and nothing obliges a manufacturer to say which grade is in the jar. In the same 1996 paper, Kligman bought "Vaseline" at six Philadelphia pharmacies; three turned out to be unbranded greases of unknown composition, and those three WERE comedogenic in his revised rabbit model. A tub of unspecified petroleum grease is not the material that was tested, and the word on the label cannot tell the two apart. Our Clear attaches to the refined material. It cannot attach to a supply chain we cannot see. There is a human counter-signal, and it should not be waved away. In 1970 Plewig, Fulton and Kligman described "pomade acne" in Archives of Dermatology — comedones concentrated on the foreheads and temples of Black men using greasy hair-grooming products — and Vaseline was named among the products implicated. Kligman's 1996 rebuttal to this is the counterfeit-product story above: an anecdote from six pharmacies, not a study. So the human record contains one observational report associating petrolatum-type greases with comedones and one small uncontrolled trial finding refined petrolatum non-comedogenic on the face. We weight the trial, because it measured the thing directly. We are not going to pretend the first report does not exist. On the safety fear, which is a separate question from the pore-clogging one and is usually the real reason people avoid this ingredient: the concern is polycyclic aromatic hydrocarbons, and it is a concern about refining, not about hydrocarbons as such. Under EU cosmetics law petrolatum is banned unless its full refining history is known and the substance it was produced from is not a carcinogen; the European Commission's own statement of that rule adds that highly refined petrolatum is free from PAH contamination. That is a real restriction and it is the answer to the carcinogen fear — in the EU. It is a restriction on the SUPPLY CHAIN, not a claim carried by the word on the label, it is a European rule rather than a universal one, and it says nothing about comedogenicity in either direction. We have found no study testing the claim that petrolatum "suffocates" skin, and we are not going to assert its opposite without one. Finally, the field-wide caveat applies here as everywhere: a 2025 review in JAAD Reviews found that no standardised comedogenicity test exists and that "non-comedogenic" is an unregulated label. Petrolatum has better evidence behind it than anything else we rate. That is a statement about how thin the rest of the evidence is.
Where you’ll see it
Ointments and healing balms, lip balms, barrier and diaper creams, eye ointments, and occlusive night routines. It appears on labels as Petrolatum, Petroleum Jelly, White Petrolatum or Soft White Paraffin, and unlike most ingredients people worry about, it is usually near the top of the list — petroleum jelly is essentially the neat material, and the emulsion Kligman tested was 30%. It is distinct from Paraffinum Liquidum (mineral oil), which is the liquid member of the same hydrocarbon family and a different entry.
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.
- 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 primary source, read in full. 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 at 0 and 8 weeks. Neither comedones nor microcomedones increased. The same paper re-runs the rabbit-ear assay with untreated-ear controls and finds the 1972 petrolatum result was a false positive. Small and uncontrolled — but human, on faces, measuring the right endpoint, and a self-correction by the investigator who made the original accusation. NOTE WHAT IS NOT IN IT: it grades nothing on any numeric scale, so it cannot be the source of a "legacy score" — we used to say it was — and it contains no lanolin experiment, which is a claim we also had to retract from another page.
- 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, from a different laboratory, continent and decade — and we had omitted it, which meant this page claimed no replication existed. Eight acne-prone women, petrolatum from Sigma, 0.3 mL over 16 cm², three times weekly for four weeks under occlusion, microcomedones counted by cyanoacrylate follicular biopsy. Petrolatum: +55%. A control site with no test material on it at all: +54%. No significant difference. The paper was not designed to exonerate petrolatum — it was asking whether the standard positive controls work in Asian skin — which is part of why it is worth something: petrolatum was not the point of it.
- Kligman AM, Mills OH. "Acne cosmetica." Arch Dermatol 106:843–850 (1972) The original indictment. The rabbit-ear paper that coined "acne cosmetica," reported that about half of commercial cosmetics were comedogenic, and found petrolatums and mineral oils uniformly comedogenic. It is the ancestor of the fear, and it is the paper whose method its own author later repudiated — he called its positives for the bland greases false positives, and published a corrected assay. He did not formally retract it; there is no retraction notice, and the word matters. Cited here as the thing the evidence overturned, not as support.
- Plewig G, Fulton JE, Kligman AM. "Pomade acne." Arch Dermatol 101:580–584 (1970) Human observational report describing comedones on the foreheads and temples of Black men using greasy hair-grooming products, with Vaseline named among the products implicated. Cited as the counter-signal, honestly: it is the strongest human evidence pointing the other way, it is observational rather than controlled, and the products involved were mixtures, not neat pharmacopoeial petrolatum.
- Draelos ZD, DiNardo JC. "A re-evaluation of the comedogenicity concept." J Am Acad Dermatol 54:507–512 (2006) Peer-reviewed human work on finished products, independent of Kligman. Found that cosmetic products tested non-comedogenic in humans despite containing ingredients the rabbit-ear assay had scored as comedogenic, and argued that rabbit-ear results do not reliably predict comedogenicity in human skin. It corroborates the direction of the 1996 finding — that the assay over-calls — without being about petrolatum specifically.
- European Commission, joint answer to Written Questions E-008297/2016 and E-009099/2016 (1 March 2017), on petrolatum under Regulation (EC) No 1223/2009 Primary regulatory source, cited for the safety fear rather than the pore-clogging question. States plainly that petrolatum is banned in EU cosmetics unless the full refining history is known and the substance it is produced from is not a carcinogen, and that highly refined petrolatum is free from polycyclic aromatic hydrocarbon contamination. This is the specific answer to the "petroleum by-product" fear, and it is a legal restriction, not an industry reassurance.
- "Comedogenicity in cosmeceuticals: A review of clinical relevance, regulatory gaps, and future directions." JAAD Reviews (2025) Recent peer-reviewed review of the whole field. Finds that no standardised comedogenicity test exists and that the "non-comedogenic" label is unregulated. Independent of both Kligman and the ingredient lists that republish Fulton. Cited for the field-wide caveat, which applies to this page as much as to any other.
- acne.org comedogenic ingredient list and its long-form companion article Republishes the Fulton 1989 rabbit-ear scores. Not an independent measurement, and the same is true of CosDNA, Face Reality, Banish and Sofie Pavitt — they are one assay quoted five times, not five sources agreeing. Cited here for one reason: in its own long-form article, acne.org states that petroleum jelly would qualify for its avoid list under its own rules and is excluded specifically because of Kligman's 1996 reappraisal. The republisher concedes the point.
Others in the same family
Hydrocarbons 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 hydrocarbons as a family ›
Last reviewed 2026-06-24 · How we decide