While this term is pretty standard in the beauty industry at this point, it’s not without fault. Namely: Experts can’t seem to agree on a standard practice to rate and rank ingredients. There are “comedogenic scales” and lists out there, but each varies quite a bit, and none function as an official tool used by dermatologists or cosmetic chemists. So what we’re left with is sifting through the research—or in some cases, anecdotal evidence—to figure out what ingredients are more likely to cause clogged pores. Additionally, the term isn’t regulated by the FDA, so brands are free to use it as a marketing tool, even if their formula could trigger breakouts (which breeds mistrust for the consumer).

To understand how we got here, it’s important to understand this history of the concept. The comedogenic scale (ranking from 0 to 5) was first established in the ’70s by dermatologist Albert Kligman, M.D., who actually helped pioneer Retin-A. In it, the researchers used the rabbit ear model. This is enough to give pause for a few reasons, says cosmetic chemist Krupa Koestline. The first is that rabbit ears are far more sensitive than human skin, and thus what might trigger acne on the animal might be just fine for human use. The second reason is that no modern literature has been done to confirm this test’s efficacy of use.   

Finally, it’s always worth noting that everyone is unique. We can make informed guesses about what might work for a certain skin type, but ultimately we can never fully know how skin is going to react to something. “Even if two people are predisposed to acne, what is noncomedogenic to one person might be so for another,” says board-certified dermatologist Mona Gohara, M.D. One of the main factors is skin sensitivity. Those with easily irritable and acne-prone skin might be triggered by more products than those with just oily skin. But there’s a whole breadth of other issues, including how easily your pores clog, pore size, and how quickly your skin self-exfoliates.