When you have acne, slathering anything all over your skin can feel like a game of Risk. What if it makes your already-oily skin feel greasier? What if it clogs your pores and gives you more breakouts? The skincare struggle is real.

The reigning school of thought on the subject tells us to look for the term “non-comedogenic” on product labels. But what does that even mean? Is it a guarantee you won’t get zits?  Do products labeled as such actually treat acne? We tapped the wisdom of James Del Rosso, D.O., adjunct clinical professor of dermatology at Touro University Nevada in Henderson, NV and an Acne Store advisory board member, to shed some light on this sometimes-confusing term.

What does non-comedogenic mean?

First, let’s talk about what a comedone is. It’s basically dermatologist speak for a clogged pore. On the skin’s surface, comedones are skin-toned, hard bumps. They can also be blackheads, which skin docs refer to as open comedones, because you can see into the pore. Dirt, debris, and dead skin lodged in the pore create the dark appearance. So, the definition of a product that is comedogenic is something that clogs pores and promotes comedones. Non-comedogenic products and ingredients do the opposite.  “If you see non-comedogenic listed on a label, it should mean the brand has done their homework, and it’s not likely to cause acne in the vast majority of people,” says Del Rosso. “It means they’ve excluded what is know, from experience or through testing, will promote comedones."

It doesn’t mean the product will treat your acne, but in theory, it shouldn’t cause it. But here’s where it gets tricky: the term non-comedogenic still does not guarantee that you won’t wind up with pimples. Keeping reading to find out why.

How are products tested to be non-comedogenic?

The classic test for comedogenicity was done on rabbit ears, called a rabbit ear assay, says Del Rosso. Rabbit ears are said to be even more sensitive to forming comedones than human skin, so if an ingredient or product caused comedones on the animal’s skin, there’s a good chance it would do the same on a human. But that type of testing has fallen out of fashion as the industry has heeded calls to stop testing on animals.

These tests are now performed on human subjects, and that’s where things get complicated. “To do human testing, you have to get humans to volunteer to have patches put on their back for a prolonged period of time,” says Del Rosso. The back isn’t nearly as sensitive to comedone formation as the face. “So, the methodologies are somewhat inconsistent, but certainly better than doing nothing,” he says.

Ingredients or products tested are then ranked on a scale of comedogenicity, usually from 0 to 5, with the higher numbers being more likely to clog your pores. Some examples of potentially comedogenic ingredients are some grades of avocado oil, beeswax, acetylated lanolin, coconut oil, and shea butter. Anything that scores a 2 or under is less likely to cause breakouts. Those that make the cut include grapeseed oil, almond oil, ascorbic acid, and cetyl alcohol. But while knowing where an ingredient lands on the comedogenic scale may be a good starting point, it still doesn’t mean you will or won’t break out, says Del Rosso.

That’s because there are limits to comedogenicity testing

The biggest issue with comedogenicity testing is that there doesn’t seem to be a standard or a widely accepted method or definition. Not everyone uses the number rankings. This leaves a lot of room for interpretation—and error. Also, it doesn’t always take into account the formulation of the product. Some ingredients that are considered non-comedogenic in low concentrations may clog pores in higher concentrations.

Another problem is a lack of checks and balances on these tests. “To my knowledge, the claims on a product do not have to be substantiated,” says Del Rosso. The FDA does not regulate them, so a brand can say a product is non-comedogenic without necessarily having done the appropriate testing.

What’s an acne-prone person to do?

Searching for the term non-comedogenic on a label is a good starting point when selecting a product for your skin, but it’s still not a guarantee that you won’t get a breakout. For that reason, Del Rosso says it’s best to go with well-known, reputable brands that have a demonstrated history of living up to their claims. “Companies that are recognized cosmetic companies have enough experience over the years to formulate a quality product that’s not going to cause acne in the vast majority of people,” Del Rosso says. “I think a lot of it is based on the quality of the formulation and the know-how of the formulator.”

Above all, it may take a bit of trial and error to know whether or not a product works for your acne-prone skin. If you’re using something new and noticing some new comedones, blackhead, or whiteheads, take a break to see if your skin improves.