Bought a new moisturizer that looked perfect on paper, only to break out within a week? There’s a good chance one of its ingredients had a high comedogenic rating — a number that quietly predicts how likely an ingredient is to clog your pores, long before you ever apply the product.
Two weeks into a new retinol routine, your skin looks worse instead of better — and now you’re facing a decision that trips up almost every beginner: is this purging, a normal part of retinol doing its job, or is your skin actually reacting badly to something? Get this wrong in either direction, and you either quit right before retinol starts working, or you keep pushing through a genuine reaction that’s damaging your skin barrier.
Understanding this rating can save you from repeating the same breakout cycle every time you try a new product. Here’s exactly what it means, where it comes from, and — just as important — where it falls short.
Comedogenic rating is a numerical scale, typically from 0 to 5, that ranks how likely a skincare ingredient is to clog pores and form comedones — the technical term for whiteheads, blackheads, and the small trapped bumps under skin that haven’t fully surfaced yet.
Most everyday skincare ingredients actually fall somewhere in the middle — between 1 and 3 — which is exactly why the scale can feel confusing to apply in real life. A product isn’t simply “safe” or “unsafe” based on one ingredient; it’s a spectrum.
“Non-comedogenic” generally refers to ingredients rated 0, 1, or 2. It’s a term you’ll see on product labels constantly, but it isn’t a regulated or standardized claim — brands can use it based on their own interpretation of the scale, which is one reason the same product can be labeled non-comedogenic by one company and flagged as pore-clogging by an independent ingredient database.
The scale traces back to research from the 1970s and 80s. Dermatologist Albert Kligman, also known for co-inventing Retin-A, developed the original testing method — applying undiluted ingredients to the inside of rabbit ears and observing how many comedones formed over several weeks. Later, in 1989, dermatologist James Fulton published what’s become the most widely cited comedogenic ingredient list, ranking hundreds of common cosmetic ingredients using this same 0–5 framework. Most comedogenic charts you’ll find today, including many still referenced online, trace back to this original research.
This is the part most sources leave out, and it matters just as much as the rating itself.
The original testing was done on rabbit ears, which are significantly more reactive and sensitive than human facial skin. An ingredient that caused visible comedones on a rabbit ear may cause little to no reaction on actual human skin — especially once it’s diluted within a finished formula rather than applied undiluted.
A high-comedogenic ingredient rarely appears in a product at full concentration. It’s typically blended with other ingredients that can offset or dilute its pore-clogging potential. This means a product containing a small amount of a “3-rated” ingredient may behave very differently than that ingredient would on its own.
Comedogenic ratings are population-level averages, not a guarantee for any one person. Oily and acne-prone skin tends to be more reactive to comedogenic ingredients than dry or normal skin, meaning the same product can clog one person’s pores while doing nothing to another’s.
An ingredient in a cleanser that’s rinsed off within seconds has far less time to clog pores than the same ingredient in a moisturizer or serum left on skin overnight. Comedogenic ratings don’t distinguish between these use cases, even though the actual risk differs significantly.
Even with its flaws, the comedogenic scale remains one of the most useful starting points for anyone dealing with clogged pores, blackheads, or acne cosmetica — breakouts caused specifically by cosmetic products rather than internal factors like hormones.
It’s especially useful when:
Used as a general guide rather than an absolute rule, checking comedogenic ratings before trying a new product can meaningfully cut down on the breakout guesswork that usually comes after the fact, once the damage is already visible.
If you’d rather skip manually cross-referencing every ingredient list against a chart, our Comedogenic Rating Checker does this lookup for you — enter an ingredient or product and get a clear read on its pore-clogging potential before it ends up in your routine.
Comedogenic rating is only one piece of building a routine that doesn’t backfire. It’s worth pairing with a clear understanding of your actual skin type, since oily, dry, combination, and sensitive skin all tolerate comedogenic ingredients differently — what causes breakouts on oily skin may sit fine on dry skin. If you’re not sure which category you fall into, our Skin Type Quiz takes about two minutes and gives you that baseline before you start filtering products by comedogenic score.
A rating of 0 means the ingredient has essentially no known potential to clog pores, based on existing research and testing.
Not necessarily. Ratings of 0–2 are generally considered safe for most skin types, including acne-prone skin, though individual reactions can still vary.
No. Concentration, formulation, and how the ingredient interacts with the rest of the product all affect the actual risk, which is why a single moderately-rated ingredient doesn’t automatically make a product unsafe.
No. “Non-comedogenic” is not a standardized or regulated label, so ratings and claims can vary between brands and sources.
Not automatically — it depends on your skin type, how the ingredient is formulated in the product, and whether it’s a leave-on or rinse-off product. Oily and acne-prone skin benefits most from being cautious with higher-rated ingredients.
Comedogenic rating gives you a science-based starting point for predicting whether an ingredient is likely to clog your pores — but it’s a guide, not a guarantee. Rabbit-ear testing, formulation differences, and individual skin variation all mean the number on a chart won’t always match what happens on your specific face. Used sensibly — checking full ingredient lists, weighing product type, and factoring in your own skin type — it’s still one of the most practical tools available for cutting down on unexplained breakouts.
