Comedogenic checker
and what the ratings mean
Paste an ingredient list to see which ingredients may clog pores (comedogenic), the 0–5 rating each source gave, and how many sources agree.
Checks as you paste. Your list stays in your browser.
The 0–5 scale
Researchers rubbed each ingredient on a rabbit's inner ear for two to three weeks, then looked at the pores under a microscope. They graded what they saw from 0 to 5. Morris and Kwan described each grade this way:
| Rating | Band on this site | What the pores looked like |
|---|---|---|
| 0 | None | Normal, same as the untreated ear |
| 1 | Low | A slight build-up of skin cells in the pore |
| 2 | Low | A clear build-up, the pore lining starting to thicken |
| 3 | Moderate | Pores stretched by a plug of skin cells |
| 4–5 | High | Pores packed and widened, sometimes inflamed |
Fulton read the same scale more simply: 0–1 is not significant, 2–3 is borderline, and 4–5 is a positive result. On this site a rating of 2 or more counts as "flags it".
Check a product in three steps
- Find the list. It's on the box or back label, or on the product's web page, after the word "Ingredients".
- Copy it. Copy the whole list from the web page, or type it from the box. Spelling mistakes are fine; the checker finds close matches.
- Paste it above. Results show up right away, in label order. Ingredients near the top usually make up more of the product.
Highest-rated in the studies
These ingredients scored highest in Fulton 1989. Where Morris and Kwan tested the same ingredient, their rating is next to it. Notice how often the two disagree.
| Ingredient | Fulton 1989 | Morris & Kwan 1983 |
|---|---|---|
| Isopropyl myristate | 5 | 3–4 (50% in propylene glycol) |
| Isopropyl isostearate | 5 | 4 |
| Myristyl myristate | 5 | 0–1 (50% in mineral oil) |
| Laureth-4 | 5 | — |
| Oleth-3 | 5 | — |
| Isopropyl linoleate | 4 | 4–5 |
| Acetylated lanolin alcohol | 4 | 4–5 |
| Isopropyl palmitate | 4 | 3 |
| Ethylhexyl palmitate | 4 | 2–3 (as octyl palmitate) |
| Cocoa butter | 4 | — |
| Decyl oleate | 3 | 3 |
A rating is a starting point
A high rating tells you an ingredient clogged pores in a sensitive lab test. It doesn't tell you what a product will do on your face.
- Rabbit skin reacts more. A 1982 study that compared the rabbit test with a test on people found the rabbit more sensitive.
- Strength matters. The tests used raw ingredients, often stronger than in a finished product.
- The formula matters. Other ingredients can change how one behaves. In Fulton's tests, the same red pigment rated differently depending on what it was mixed into.
For the details
Fulton (1989) graded about 220 ingredients at 10% in propylene glycol, a carrier that evaporates and leaves the ingredient behind. He also scored irritancy separately. Morris and Kwan (1983, Revlon Research Center) graded about 30, mostly undiluted, by microscope only.
Both papers note that results vary between labs, rabbits and raw-material suppliers. Fulton marks several results as depending on the source of the raw material, and gives lower numbers for some refined oils.
Questions
What is a comedogenic rating?
It is a number from 0 to 5 for how strongly an ingredient clogged pores in a lab test. 0 means no change. 4 or 5 means the pores filled with hard plugs. Most ratings come from tests on rabbit ears in the 1980s.
Is coconut oil comedogenic?
Many lists say coconut oil is rated 4. That number comes from Fulton 1989, but the row it comes from is coconut butter, not coconut oil. Neither study we use tested coconut oil. Our checker shows coconut oil only with the sources that actually name it.
Will a product with a high-rated ingredient break me out?
Not necessarily. The tests used raw ingredients, often at strengths far higher than in a product, on skin that reacts more than a human face. A flag is a reason to patch-test, not a verdict.
Why do sources give different numbers for the same ingredient?
They tested differently. Fulton mixed each ingredient to 10% in propylene glycol, while Morris and Kwan mostly used it pure, and the people grading the results also differed. Myristyl myristate scored 5 in one study and 0–1 in the other.
What to do next
- Patch-test first Try a new product on a small area.
- Give it a few weeks Skin takes time to show changes.
- See a doctor if it hurts Painful or widespread acne needs care. NHS · AAD
Not medical advice. Flags are a screening aid, not a diagnosis. The amount and the formula both matter.