Porecelain

Flawless skin starts with the fine print.

Propylparaben

Propylparaben is rated Clear, and the 0 behind it is a reading rather than an inference: Fulton's 1989 rabbit-ear survey printed a row under this material's own name and scored it 0 of 5. It is still one number, from three rabbits, in a model its own author called not definitive — and the argument the world actually has about parabens is about endocrine activity and contact allergy, neither of which is a pore.

Clear Low confidence Legacy score 0 on a 0-5 scale · Fulton 1989 · low reliability

Fulton 1989 rabbit ear 0 of 5, one of three paraben rows all reading 0.

What it is

Propylparaben is the propyl ester of para-hydroxybenzoic acid — propyl 4-hydroxybenzoate, CAS 94-13-3, EC 202-307-7, Ph. Eur. Propylis Parahydroxybenzoas. The EU's CosIng entry lists its cosmetic functions as preservative and perfuming, and the first of those is what a formulator reaches for: it suppresses the moulds, yeasts and bacteria that would otherwise spoil a water-containing cream. It differs from methylparaben only in the length of that ester chain — propyl rather than methyl. Hafeez and Maibach describe the parabens as a whole as the most widely used preservatives in cosmetic, pharmaceutical and industrial products. It carries a restriction that methylparaben does not. Under Commission Regulation (EU) No 1004/2014, which amended Annex V of the EU Cosmetics Regulation, propylparaben and butylparaben are capped at 0.14 per cent as the acid, individually or combined — down from the 0.4 per cent that had applied to each — and are not permitted in leave-on products intended for the nappy area of children under three. That cap was set on endocrine grounds, not comedogenic ones. It matters here only because it fixes how much of this material can legally be in a European product, which is a useful number to hold beside the concentration the assay used.

Why we rate it Clear

We rate propylparaben Clear at Low confidence. The Low records what the evidence is — a single legacy rabbit-ear assay, and nothing else we could find that measured comedones. The Clear records what that assay returned. Fulton's 1989 survey, the source most circulating comedogenic numbers descend from, scored propylparaben 0 on its 0–5 scale. We read the row off a 400dpi render of the journal scan rather than from a list quoting it: "Propylparaben 0", spelled as one word, with no asterisk and no range. This is the check that matters most on this site and it comes back clean here — the name in the table is the material, not a neighbour, a derivative or a differently-processed grade. Fulton's own published key reads 0–1 "not considered significant", 2–3 "borderline", 4–5 "considered positive", so a 0 is the floor of the scale. The method behind that 0 is the method behind every Fulton number: the ingredient diluted to roughly 10 per cent in propylene glycol, 1 mL applied to the inner ear of three New Zealand albino rabbits, the follicles then examined for keratosis. Two things follow, and they pull in opposite directions. The concentration was high — roughly seventy times the 0.14 per cent an EU product may now contain — though we hold no measured in-use figure for what a finished product carries. And the ear was a rabbit's, scored by one investigator, in a model he warned was so sensitive that not everything which irritates it will irritate human skin. What the row does not carry is a supplier, a purity or a grade, so it establishes that a material called propylparaben was on the bench in 1989, not which one. Fulton's table prints three paraben rows — methyl paraben, propylparaben and phenoxyethyl paraben — and all three read 0. We note that because the third of them is the source of a real error elsewhere: phenoxyethanol, a different preservative with no row of its own anywhere in the paper, is widely credited with a 0 that no document we hold assigns it. Whether it was lifted off this row is a guess nobody has traced, and our phenoxyethanol page declines to make it. Propylparaben has its own row, and it does not need to borrow. INCIDecoder, which publishes a per-ingredient comedogenicity figure without stating a method, prints 0 for propylparaben. That is not a second measurement, and we are not counting it as corroboration. It is the ordinary case in which a consumer checker's number and a measured number happen to be the same.

What the evidence doesn’t tell you

A 0 in this model is the absence of an effect in three rabbits, at one concentration, on one occasion. Fulton wrote of the survey itself that it "is not at all definitive but simply designed to stimulate research". It is not a controlled human result, and we identified no human comedogenicity study of propylparaben. We identified no second assay of it either, and checked rather than assumed. Morris and Kwan's 1983 rabbit-ear study — an independent laboratory, and the one legacy paper that contradicts Fulton in print on other materials — tested 32 substances: seven lanolins, nine vegetable oils, eleven esters and five surfactants, no paraben among them. Fulton's own earlier 1984 survey carries no paraben row. The fourteen materials named in the abstract of Nguyen, Dang and Maibach's 2007 rabbit-ear study include no paraben. For the Kligman-lineage papers and for Lanzet 1986 we do not hold complete material lists, so our statement there is narrower still: we found no report of a paraben in them. The 0 therefore stands alone. It has not been confirmed and it has not been contradicted, and silence is not agreement. Human skin testing of propylparaben does exist, and it measured something else. Hafeez and Maibach report Marzulli and colleagues patch-testing methyl- and propylparaben at concentrations up to 20 per cent in petrolatum in 397 healthy volunteers; the endpoint was contact sensitisation, and the index was 0.3 per cent. That is a study of allergy, not of follicles. No comedones were counted in it, and it can tell you nothing about pores in either direction. The same separation applies to everything else parabens are argued about. The SCCS's 2021 final opinion on propylparaben concluded it safe as a preservative up to 0.14 per cent, and found the available data gave "some indications for potential endocrine effects" while judging the evidence insufficient to class it as an endocrine disruptor. That is a systemic-safety judgement. A safety conclusion is not evidence of noncomedogenicity, and an endocrine question is not a pore question; reading either as the other would be the category error this site exists to catch, run in reverse. A 2025 review of the comedogenicity field reports that no standardised comedogenicity test exists and that "non-comedogenic" is an unregulated label. That ceiling sits over this page as it sits over every page here, including the ones with a measured number on them.

Where you’ll see it

On a label it reads Propylparaben. In the EU its concentration carries a legal ceiling of 0.14 per cent as the acid, alone or with butylparaben, and it may not be used in leave-on products for the nappy area of children under three. We hold no measured in-use figure for it. Where a name falls on an ingredient list is not a dose, and it is not a comedogenic signal either.

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. Fulton JE. "Comedogenicity and irritancy of commonly used ingredients in skin care products." J Soc Cosmet Chem 40:321–333 (1989) The rabbit-ear survey most circulating comedogenic numbers descend from, read here off a 400dpi render of the journal scan rather than through a list quoting it. Method: ingredient diluted to roughly 10% in propylene glycol, 1 mL to the inner ear of three New Zealand albino rabbits, follicles scored for keratosis on a 0–5 scale whose own key reads 0–1 "not considered significant", 2–3 "borderline", 4–5 "considered positive". Cited as the primary and direct evidence for this rating: Table I prints "Propylparaben 0" — the material itself, not a neighbour or a derivative — with no asterisk and no range. Fulton called the survey "not at all definitive". It is a single reading in one animal model, by one investigator, and it is the whole of the measured comedogenic evidence we hold for this ingredient.
  2. 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 laboratory's rabbit-ear assay on the same 0–5 scale, predating Fulton 1989 and contradicting it in print on several materials — which is why it is not simply a republisher of him. Its 32 test materials were seven lanolins, nine vegetable oils, eleven esters and five surfactants. Cited here for a bounded absence only: no paraben is among them, so it offers propylparaben's 0 no corroboration and no contradiction.
  3. 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, on a 0–5 scale with a different key — 1–2 not significant, 3 or above positive — which is not the 1989 key and cannot be read alongside it. Cited here only for an absence: its table carries no paraben row, so it adds no second reading of propylparaben in either direction.
  4. Nguyen SH, Dang TP, Maibach HI. "Comedogenicity in rabbit: some cosmetic ingredients/vehicles." Cutan Ocul Toxicol 26(4):287–292 (2007) A later rabbit-ear study on a 0–4 scale — a third scale, easy to misread as Fulton's. Only its abstract has been read; the abstract names the fourteen test materials, and no paraben is among them. Cited for that absence only.
  5. Cosmetic Ingredient Review Expert Panel. "Final Amended Report on the Safety Assessment of Methylparaben, Ethylparaben, Propylparaben, Isopropylparaben, Butylparaben, Isobutylparaben, and Benzylparaben as Used in Cosmetic Products." Int J Toxicol 27(Suppl 4):1–82 (2008) The industry expert-panel SAFETY dossier covering propylparaben by name. Its document state is not recorded here — we hold no note of which version was read, or when — so nothing is claimed about whether the text consulted was final, tentative or draft. Cited only for identity and function. It assesses safety, sensitisation and systemic exposure; it counts no comedones, and a safety conclusion is not evidence of noncomedogenicity in either direction.
  6. Scientific Committee on Consumer Safety. "Opinion on Propylparaben (CAS No 94-13-3, EC No 202-307-7)", SCCS/1623/20, final opinion adopted 30–31 March 2021 A European regulatory risk assessment in its FINAL state, later published in Regul Toxicol Pharmacol. It concludes propylparaben safe as a cosmetic preservative up to 0.14%, and reports "some indications for potential endocrine effects" that it judges insufficient to class the substance as an endocrine disruptor. Its endpoints are systemic toxicity and endocrine activity. It did not test comedogenicity and is cited here only for the concentration ceiling and for what the paraben argument is actually about.
  7. Commission Regulation (EU) No 1004/2014 of 18 September 2014 amending Annex V to Regulation (EC) No 1223/2009 of the European Parliament and of the Council on cosmetic products Legislation, not evidence. It sets the current EU maximum for propylparaben and butylparaben at 0.14% as the acid, individually or combined, replacing the previous 0.4% single-ester limit, and excludes them from leave-on products for the nappy area of children under three. Cited for the legal use concentration, which is the number Fulton's roughly 10% assay concentration is compared against. The restriction was made on endocrine grounds; it says nothing about pores.
  8. Hafeez F, Maibach HI. "An Overview of Parabens and Allergic Contact Dermatitis." Skin Therapy Lett 18(5):5–7 (2013) A narrative review of four decades of paraben patch-testing, which states outright that it does not address the separate endocrine controversy. Not new data and not a comedogenicity paper. Cited for two things: that parabens are the most widely used preservatives in cosmetic, pharmaceutical and industrial products, and its report of Marzulli and colleagues patch-testing methyl- and propylparaben up to 20% in petrolatum in 397 healthy volunteers for a 0.3% sensitisation index — human skin data whose endpoint was allergy, with no comedone count anywhere in it.
  9. Consumer ingredient checkers (INCIDecoder, and similar) Aggregators that publish a per-ingredient comedogenicity figure with no method stated on the ingredient page and no citation attached to the number. INCIDecoder lists propylparaben at comedogenicity 0 and irritancy 0. Cited to record what a reader will find, not as evidence: a matching number is not a second measurement, and we did not trace where this one was taken from.
  10. "Comedogenicity in cosmeceuticals: a review of clinical relevance, regulatory gaps, and future directions." JAAD Reviews (2025) A recent peer-reviewed review of the comedogenicity field from 1972 onward. A synthesis of the same legacy literature, not a new measurement, and independent of Fulton only in authorship. Cited for one field-wide caveat: no standardised comedogenicity test exists, and "non-comedogenic" is an unregulated label. It sets the ceiling on how much any comedogenic number can be asked to carry.

Others in the same family

Preservatives 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 preservatives as a family ›

Last reviewed 2026-08-20 · How we decide

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