Is It Comedogenic? What Pore-Clogging Ratings Can and Can't Tell You
That 0-to-5 comedogenic rating you just looked up comes from a 1989 study done on rabbit ears, not human faces. Here's what the number can actually tell you, what it can't, and a practical way to check any label and your own skin instead of trusting a chart.
Quick Answer
Question: What does a comedogenic rating actually tell you, and can you trust it?
Answer: A comedogenic rating is a 0-to-5 score most lists trace back to a 1989 study where ingredients were applied to the inside of rabbit ears, not human skin. A high number is a reason to pay attention, not proof a product will clog your pores, and a low number is not a guarantee either. The most reliable test is reading the full label and watching your own skin over several weeks.
The Situation You're In
You searched a comedogenic rating because something gave you small bumps, or you're holding a product you want to buy and you're trying not to repeat a mistake. You found a chart with tidy numbers next to ingredient names, and now you're trying to figure out whether that 4 next to one of your ingredients actually means anything.
Here's a quick thing you can do right now: flip your product over and read the back label, not the claims on the front. See if you can spot where an ingredient sits in the order, because that matters more than you'd think, and I'll explain why below.
Why This Happens
The comedogenic scale feels scientific because it's a number, and numbers feel like answers. The 0-to-5 grades most online lists use come from a 1989 study by James Fulton, published in the Journal of the Society of Cosmetic Chemists. Each ingredient was applied to the inside of a rabbit's ear at 10% strength, five days a week for two weeks, then graded on how badly the follicles plugged up. That's where your chart comes from.
The problem is what the chart leaves out. Fulton himself wrote that the rabbit ear is extremely sensitive and that not everything which reacts on it will react on human skin. So the test was useful for flagging suspects, not for predicting your face. Later work complicated it further: a small 2006 study by Draelos and DiNardo in the Journal of the American Academy of Dermatology tested finished products containing high-rated ingredients on actual people (only six of them) and found they weren't necessarily comedogenic. Fulton himself did not accept that a lower concentration makes a high-rated ingredient safe, so the honest reading cuts both ways: a high rating is a reason to pay attention, and a low one is not a guarantee.
And then there's the telephone-game problem. A lot of comedogenic lists online repeat values that aren't even in Fulton's original table. The classic example: coconut oil gets passed around as "a 4 from Fulton," but Fulton's table lists coconut butter, not coconut oil. So some of the scary numbers people cite were never measured the way the chart implies. This is exactly the kind of thing we run into constantly at Seoul Sister when we cross-check what's actually printed on a label against what the internet claims about it.
What Actually Works
The honest move is to stop treating the rating as a verdict and start using it as a starting point, then let your own skin be the final test. Here's the method.
Read the full ingredient list on the back, and pay attention to order. The claims on the front ("pore-friendly," "lightweight," even "non-comedogenic") tell you less than the actual list. On a US cosmetic, ingredients above 1% are listed from most to least, so an ingredient near the top carries more weight than one near the very end. One exception: if the product is a US acne treatment with a "Drug Facts" panel, its inactive ingredients are listed alphabetically, so order tells you nothing there.
Know the handful of ingredients Fulton graded highest, as a watchlist, not a blacklist. The six that Fulton graded 4 or 5 in his 1989 rabbit-ear test are isopropyl myristate (5), myristyl myristate (5), laureth-4 (5), isopropyl palmitate (4), ethylhexyl palmitate (4), and isostearyl isostearate (4). Seeing one high on a list is a reason to watch how your skin responds, not a reason to toss the product. For contrast, Fulton graded squalane a 1 and dimethicone a 1, both of which show up constantly in Korean skincare. You can read the full breakdown on our pages for isopropyl palmitate, squalane, and dimethicone. Knowing the six is a starting point, not a complete list.
Use format as a clue, not a rule. As of November 2026, across Seoul Sister's catalog of 5,240 Korean skincare products with ingredient lists, about 9% list at least one of those six ingredients (488 products). That share isn't even across categories. Sun sticks list one about half the time (36 of 72), while other sunscreen formats like creams and cushions sit around 6% (35 of 544). Cleansing oils and balms land at 57% (120 of 210), lip care around 23%, and toners under 2%. To be clear, those are counts of what's printed on labels, not breakout rates on anyone's face. But if you suspect a sunscreen and it happens to be a stick, the format is worth knowing, because sticks list these far more often than other formats do.
Change one thing at a time and give it real time. Reactions can take weeks to months to show up on human skin, so a product isn't "safe" just because nothing happened in the first week. Introduce one new product, wait several weeks, and keep a simple note of what you started and when. If new small bumps appeared after starting something, the newest product is the first suspect. The exception: if the newest thing is an acne treatment like a retinoid or benzoyl peroxide and you were told to expect an adjustment period, check with the pharmacist or doctor who recommended it before stopping. If you want to understand why order and timing matter so much when a routine goes sideways, this walkthrough on why skincare keeps making skin worse goes deeper, and if you're not sure whether those bumps are even breakouts, sebaceous filaments versus blackheads is worth a read before you blame an ingredient.
One more thing worth knowing: a product reformulating silently can undo all of this. The version you've used happily for a year can change, and the change is not always obvious from the front of the box, which is its own rabbit hole, covered in why the same brand's similar product can wreck your skin.
Frequently Asked Questions
What does comedogenic rating mean?
A comedogenic rating is a 0-to-5 score estimating how likely an ingredient is to clog pores, and the grades most lists use come from James Fulton's 1989 study where ingredients were tested on the inside of rabbit ears at 10% strength. A higher number meant more severe follicle plugging in that test. It's a flag for attention, not a measurement of what will happen on your skin.
Is a comedogenic rating of 2 bad?
A rating of 2 is not inherently bad, and the number alone can't tell you whether a product will clog your pores. Fulton's own test was done on highly sensitive rabbit ears, and he noted that not everything reacting there reacts on human skin. A mid-range rating is a reason to watch your skin, not a reason to avoid a product outright.
Does non-comedogenic mean it won't clog pores?
No, "non-comedogenic" doesn't guarantee a product won't clog your pores. In the US it's a marketing claim; the FDA keeps no list of approved cosmetic claims, so these terms only have to be truthful and not misleading rather than meeting a defined standard. The American Academy of Dermatology still advises people with acne to choose products labeled "non-comedogenic" or "won't clog pores" as a reasonable starting point, but your own skin over several weeks is the final test.
How long does it take for a product to clog pores?
Pore-clogging reactions on human skin can take weeks to months to show up, so a product is not "safe" just because nothing happened in the first few days. This is exactly why changing one product at a time and watching for several weeks matters. If you swap several things at once, you lose the ability to tell which one caused the bumps.
The Bottom Line
The comedogenic scale isn't useless and it isn't gospel. It's a 1989 rabbit-ear screen that flags ingredients worth watching, and the honest way to use it is as a starting point rather than a verdict: read the full label, know the handful of high-graded names, notice format, change one thing at a time, and let your own skin decide over several weeks. If painful, deep, or scarring acne is the issue, or nothing improves after a few months, that's a dermatologist conversation, not a chart-reading one.
If you've got bumps and genuinely can't tell which product is behind them, you can paste the ingredient lists (off the box or the brand's website) into a free chat with Yuri, Seoul Sister's AI advisor, using the Ask Yuri button on this page. It's free to start, needs no account, and it'll help you compare what you're actually layering instead of guessing from a number on a chart.