Comedogenic ingredients and ingredient checkers: what the ratings mean and their limits
Where comedogenic ratings come from (1980s rabbit-ear tests), which ingredients tested positive, why 'non-comedogenic' isn't regulated, and how to use ingredient checkers sensibly.
Short answer
Comedogenic ratings come mostly from 1980s rabbit-ear tests, which are more sensitive than human skin and gave different results in different labs. They're useful for spotting ingredients worth caution, such as some isopropyl esters, but a listed ingredient doesn't make a finished product clog pores. "Non-comedogenic" isn't regulated. Use checkers as a rough filter, then judge by how your skin responds.
We may earn a commission when you buy through links on this page. It never changes what we recommend.
What this means for you
Start with what you notice
Use a rating as a reason to look closer, never as a verdict about your skin.
The ingredient names, translated
Ingredient "pore-clogging" scores mostly come from old tests on rabbit ears, which react more strongly than human skin. A flagged ingredient doesn't mean a product will break you out, and a "non-comedogenic" label isn't a guarantee because nobody regulates it. Checker apps are a starting point, not a verdict.
How to decide
- A flagged ingredient means it is worth caution, not that the product will break you out.
- A finished product is not the sum of its ingredients. Judge the formula, not the list.
- Non-comedogenic on a label is a claim from the same kind of screening, not a guarantee.
- If a product has sat on your skin for weeks and you get tiny new bumps under it, that is your own evidence.
What to expect
Expect the ratings to disagree between labs and to be weakest on the ingredients people argue about. Expect a checker to be a filter you run before you buy, and your own skin over several weeks to be the answer.
General guidance, not a test of these products: Fulton JE Jr, Pay SR, Fulton JE 3rd. Rabbit-ear comedogenicity of products and ingredients. J Am Acad Dermatol. 1984;10(1):96-105 (PMID 6229554); Mills OH Jr, Kligman AM. Human model for comedogenicity testing vs the rabbit ear. Arch Dermatol. 1982;118(11):903-5 (PMID 7138047); Tucker SB, et al. Reliability of the rabbit-ear comedogenicity assay. Arch Dermatol. 1986;122(6):660-5 (PMID 2940978); Nguyen SH, Dang TP, Maibach HI. Rabbit-ear comedogenicity re-test of cosmetic ingredients. Cutan Ocul Toxicol. 2007;26(4):287-92 (PMID 18058303); Zatulove A, Konnerth NA. Cosmetic industry use of the rabbit-ear comedogenicity assay. Cutis. 1987;39(6):521 (PMID 2956066); Boozalis E, Patel S. Clinical utility of marketing terms used for over-the-counter dermatologic products. J Dermatolog Treat. 2018;29(8):841-845 (PMID 29671667); Makeup and acne (American Academy of Dermatology); When acne won't clear (American Academy of Dermatology); La Roche-Posay Effaclar Duo (+M) Drug Facts label (FDA, via openFDA). Each product's label source is linked on its product page.
Where do comedogenic ratings come from?
The rabbit-ear test
Most comedogenicity data comes from the rabbit-ear assay: an ingredient is applied to the inside of a rabbit’s ear and the resulting comedones are graded. In an influential 1984 paper, Fulton et al. tested many cosmetic ingredients and products this way and described the rabbit ear as not an ideal animal model, but the best available.
In 1987, Zatulove & Konnerth described how the cosmetics industry adopted this test to support “non-comedogenic” claims.
Rabbit ear vs human skin
Mills & Kligman (1982) developed a human test: ingredients applied under occlusion to the upper back for a month, then checked with a follicle biopsy. They found the rabbit model is more sensitive than human skin. Substances that were only weakly comedogenic in rabbits were probably safe for human use, with the possible exception of acne-prone people.
Reliability problems
A 1986 study (Tucker et al.) noted controversy over the test’s reliability because different laboratories got different results, and said the subjective way comedones are graded may contribute.
Where the 0–5 numbers come from
Many apps and online lists give each ingredient a score from 0 to 5. We couldn’t trace exactly where each list’s numbers come from or how they’ve been updated. Treat any single number with caution, especially when lists disagree.
Skin Realist check: a comedogenic rating is about one ingredient, often tested at a set concentration on rabbit skin. Your face meets a finished product, at whatever concentration the formula uses, in combination with everything else in it. Those aren’t the same thing.
Which ingredients tested positive?
A 2007 re-test by Nguyen, Dang & Maibach is one of the clearer modern summaries.
| Tested positive (comedogenic in rabbit ear) | Tested negative |
|---|---|
| Isopropyl myristate | Cetyl alcohol |
| Isopropyl palmitate | Stearyl alcohol |
| Isopropyl isostearate | Paraffin |
| Butyl stearate | Petrolatum |
| Decyl oleate | Sodium lauryl sulfate |
| Isostearyl neopentanoate | |
| Isocetyl stearate | |
| Myristyl myristate | |
| Cocoa butter |
Fulton et al. (1984) also flagged isopropyl myristate and related esters, some acetylated and ethoxylated lanolins, and some D&C red dyes. Interestingly, they couldn’t confirm that sulfur is comedogenic, and suggested the bias against it be reconsidered.
Two common myths this corrects:
- “Fatty alcohols clog pores.” Cetyl and stearyl alcohol tested negative. They’re thickeners, not the same as oils.
- “Petrolatum clogs pores.” It tested negative in this re-test.
Is “non-comedogenic” regulated?
No. A 2018 review in the Journal of Dermatological Treatment found that “non-comedogenic”, “oil-free”, “hypoallergenic” and “fragrance-free” are not regulated by any governing body.
That doesn’t make the label useless. The American Academy of Dermatology (AAD) recommends choosing products labelled “non-comedogenic”, “oil-free” or “won’t clog pores”. But the AAD also notes that some labelled products can still cause breakouts in some people, so you may need to try a few (AAD).
A real example: Effaclar Duo
On Reddit, people said Effaclar Duo (+M) had “possibly comedogenic ingredients”. The US Drug Facts label lists isocetyl stearate and myristyl myristate among its inactive ingredients. Both tested positive in older rabbit-ear screening (Fulton 1984; Nguyen 2007).
What that does and doesn’t mean:
- It does explain why checker apps flag it.
- It doesn’t mean the finished product clogs pores. The ingredient amounts and the rest of the formula matter, and people’s skin varies.
- If you use it and your skin is clearing, there’s no reason to stop because of an app. If you’ve developed new small bumps since starting it, it’s a reasonable product to pause.
(This refers to the US label. Outside the US it’s sold as a cosmetic without a Drug Facts panel, and we haven’t checked that version’s ingredient list.)
How should you use ingredient checkers?
Ingredient-checker apps and websites compare a product’s ingredient list against a caution list. That’s useful, as long as you know what they can’t do.
What checkers do well
- quickly show whether a product contains ingredients that tested positive in screening studies
- help you compare a few similar products
- help you spot a common ingredient across products that have broken you out
What checkers can’t do
- account for concentration: ingredient lists show order, not amounts
- judge the whole formula
- predict your skin’s response
- tell you whether a product causes fungal acne, which is a different problem; see fungal acne ingredients
A sensible approach:
- Use the checker as a first filter, not a verdict.
- Watch for patterns. If two or three products that broke you out share an ingredient, that’s more useful than any rating.
- Change one product at a time and give it several weeks; the AAD notes makeup breakouts can take days to months to appear.
- Don’t discard products that work for you because an app flags them.
Our label checker lets you filter the full formulas we’ve reviewed against specific ingredients, if you want to find options without a particular ingredient you suspect.
When should you see a dermatologist?
- You’ve switched to non-comedogenic products and still get lots of small bumps
- You can’t identify a trigger after changing products one at a time
- The bumps itch or are all the same size (possible fungal acne)
Common questions
What does comedogenic mean?
Likely to cause comedones, the clogged pores that become blackheads and whiteheads. Most ingredient ratings come from rabbit-ear tests from the 1980s, which check whether an ingredient produces comedones on rabbit skin.
Are comedogenic ratings accurate?
Only roughly. Researchers found the rabbit ear is more sensitive than human skin, and a 1986 study noted results varied between laboratories partly because grading is subjective. A rating is a caution flag, not a prediction for your skin.
Which ingredients are most likely to clog pores?
In rabbit-ear re-testing, isopropyl myristate, isopropyl palmitate, isopropyl isostearate, butyl stearate, decyl oleate, isostearyl neopentanoate, isocetyl stearate, myristyl myristate and cocoa butter tested positive. Whether a product containing them affects you depends on the formula and your skin.
Do fatty alcohols and petrolatum clog pores?
Not according to rabbit-ear re-testing. A 2007 study found cetyl alcohol, stearyl alcohol, paraffin and petrolatum were not comedogenic, despite appearing on many online lists.
Is non-comedogenic regulated?
No. A 2018 review found "non-comedogenic", "oil-free", "hypoallergenic" and "fragrance-free" aren't regulated by any governing body. The American Academy of Dermatology still recommends looking for the term as a useful filter.
Are ingredient checker apps worth using?
As a rough filter, yes. They show which listed ingredients appear on their caution lists, but they can't account for concentration, the whole formula or your skin. Don't throw out a product you tolerate well because an app flags it.
Does Effaclar Duo contain comedogenic ingredients?
The US label lists isocetyl stearate and myristyl myristate, two esters that tested positive in older rabbit-ear screening. That doesn't mean the finished product clogs pores, and many people use it without problems.