Where the ratings come from
Every flag on this site names its source. Here is each source, what it tested, its limits, and how we count
agreement between them.
254 ingredients so far: 204 from a paper we read, 50 from a
list only.
A list also names 34 broader terms, such as “algae”. For fungal acne, lab growth results for 71 ingredients.
Last updated October 22, 2026.
How we count agreement
For each ingredient we show how many sources flag it, out of the sources that take a position on it. "2 of 3"
means two sources flag it and one doesn't.
- A published list takes a position on every ingredient. If the ingredient is on the list, the
list flags it. If it isn't, the list counts as not flagging it.
- A study only takes a position on the ingredients it tested. If a study didn't test an
ingredient, it isn't counted for that ingredient at all.
-
A study flags an ingredient when it rated it 2 or higher on its 0–5 scale.
The highest rating any source gave is the number you see on each result.
What the evidence labels mean
- From a paper we read
- At least one study we read in full gave a rating for this ingredient.
- From a list only
- Only published lists flag it. We haven't found a study that tested it.
- Unconfirmed
- The only rating comes from a study we haven't read in full. Treat it with care.
The pore-clogging studies
- What was tested
- Rabbit ear test, 3 rabbits, 2 weeks. Each ingredient at 10% in propylene glycol unless noted.
- Scale
- 0–5 pore-clogging grade, plus a separate 0–5 irritancy grade
- Read by us
- Yes, full text, October 22, 2026
- What was tested
- Rabbit ear test, 3 rabbits, 14 applications, graded under the microscope. Undiluted unless a dilution is given.
- Scale
- 0–5 pore-clogging grade
- Read by us
- Yes, full text, October 22, 2026
The published lists
Many clinics publish lists of ingredients they consider pore-clogging. We only use lists whose owners allow it,
and we record facts only: which ingredients a list flags, with a link back. Most lists don't say where their
ratings come from.
- Gives
- Which ingredients it flags, no numbers
- Last checked
- October 22, 2026
The fungal-acne studies
The fungal acne checker shows lab tests of the yeast behind fungal acne
(Malassezia). Each result says which species grew on an ingredient. It never gives a 0–5 rating, and we
haven't found a study that tested these ingredients on people with fungal acne.
- What was tested
- 9 lab strains of 4 Malassezia species (M. furfur, M. sympodialis, M. globosa, M. restricta), each grown on agar where the tested ingredient was the only fat. Oils at 10%, emulsifiers at 5%, fatty acids and thickeners at 2%, in dimethicone or water; liquids also undiluted. Growth checked by eye at 7 and 14 days.
- Results
- Growth or no growth, for each strain (supplementary Table S1)
- Read by us
- Yes, full text, October 22, 2026
- What was tested
- M. furfur and M. pachydermatis, one strain each, in a lab broth where one fatty acid or Tween was the only fat, with the detergent NP-40 to help the yeast take it up. 72 hours. With another detergent (Brij-58), oleic and palmitic acid gave no growth.
- Results
- Grew, or limited growth, for each species (from the article text)
- Read by us
- Yes, full text, October 22, 2026
Background, and papers read as abstracts only
We cite these on the fungal acne page for background, or have read only their summaries, so they don't
count in the checker:
-
Xu J, et al. Dandruff-associated Malassezia genomes reveal convergent and divergent virulence traits
shared with plant and human fungal pathogens. PNAS 2007;104(47):18730–18735.
doi
(background: M. globosa can't make its own fatty acids)
-
Durdu M, Güran M, Ilkit M. Epidemiological characteristics of Malassezia folliculitis and use of the
May-Grünwald-Giemsa stain to diagnose the infection. Diagn Microbiol Infect Dis
2013;76(4):450–457.
doi
(abstract only: M. globosa was the most common species in 49 patients)
-
Koyama T, et al. Effects of topical vehicles on growth of the lipophilic Malassezia species. J Dermatol Sci 2002;29(3):166–170.
doi
-
Papavassilis C, et al. Medium-chain triglycerides inhibit growth of Malassezia. Crit Care Med 1999;27(9):1781–1786.
doi
-
Mayser P, et al. Hydrolysis of fatty acid esters by Malassezia furfur. Acta Derm Venereol 1995;75(2):105–109.
doi
What a rating can't tell you
- Most ratings come from rabbit ears. The rabbit ear test (an old lab test) reacts more strongly
than human skin. Fulton, who ran the largest study, called the test very sensitive and his survey not
definitive.
- The amount matters. The two studies tested at different strengths. Fulton used 10% in
propylene glycol; Morris and Kwan mostly used the pure ingredient. That is one reason their numbers differ.
- A finished product is not a raw ingredient. An ingredient that reacts in the test may be at a
low level in a product, or the rest of the formula may change how it behaves.
- Your skin is your own. A flag is a reason to patch-test, not a verdict.
Words we use
- Comedogenic
- Likely to clog pores and cause small bumps called comedones (blackheads and whiteheads).
- INCI name
-
The official ingredient name printed on the label, such as "Butyrospermum Parkii Butter" for shea butter. We
check names against the EU's CosIng database (source: European Commission, CosIng database, CC BY 4.0; names
excerpted).
- Rabbit ear test
- A lab test from the 1970s and 80s where an ingredient is applied to a rabbit's inner ear for two to three weeks and the pores are checked under a microscope.
- Refined oil
- An oil that has been purified. Fulton found some refined oils rated lower than the crude oil.
Spotted a mistake, or know a source we should add? Tell us and name the ingredient and the
source.