Non-comedogenic: you’ve likely seen it listed on your sunscreen, face wash, moisturizer, or even your foundation accompanying additional claims such as “oil-free” and “non-irritating.” While some phrases are self-explanatory, non-comedogenic proves otherwise for the average consumer. So what does it mean? And more importantly, is the statement actually meaningful?
What Are Comedones?
Comedones are non-inflammatory acne spots that are either open (blackheads) or closed (whiteheads); more simply put, comedones are clogged pores.[1] “Non-comedogenic” therefore implies that a product will not cause clogged pores. But how is that determined?
Testing Comedogenicity
In 1941, a research group published their findings regarding the response of rabbit skin to certain substances, a test known as the rabbit model or rabbit ear assay.[2-4] No true standard operating procedure for this test exists, meaning each time it is performed it is done so with variation. Typically, the test involves applying a substance, in a specified concentration, to the inner ear of a rabbit. Rabbit ears were chosen for two principle reasons: rabbit skin is more sensitive than human skin and so results are generally produced faster, and pores in this part of the rabbit are similar to human pores.[5] The substance is generally applied once daily, sometimes with an overlying patch, for a week or longer after which the tested area is examined. This is done visually (looking for enlarged pores and comedone formation), histologically (a section of tissue is examined under a microscope), by mounts (the underside of the top layer of skin is examined under a microscope) or by weighing (the tested section is weighed first with the comedones then again after the comedones have been removed).[6] The first three methods often involve measuring the size of the comedones. A scale, usually either 0 to 3 or 0 to 5, is used to assign the severity of the comedogenic response, zero being no response and the highest number indicating a severe response.
Testing in humans is conducted by applying compounds to the upper back. After a prescribed length of time, they are evaluated by direct examination of the skin and through microscopic evaluation of biopsy collections.[7,8] Results show that while some ingredients are indeed comedogenic, the severity of the response differs between individuals. As more companies move away from animal testing, human testing becomes more important.
Problems with the Tests
The analysis of the skin response is inherently subjective, even if effort is made to make it more quantitative and objective; what may look like a severe response to one researcher may not to another, or the size/weight threshold of a large comedone could be disagreed upon. The dilution of the substance being tested, the solvent used to dilute/deliver the substance, the amount applied, how often, and for how long are all additional factors that can affect the comedogenic score.
In 1988, the American Academy of Dermatology held a symposium in an effort to make testing clearer, as well as to generally determine what should be deemed comedogenic.[9] They decided that if an ingredient was found to be non-comedogenic in rabbits, it was likely to be non-comedogenic in humans also. However, ingredients shown to produce a comedogenic response in rabbits may or may not produce one in humans. Comedogenic ingredient lists were determined to be “not necessarily meaningful.”
Individual ingredients are not predictive of how topical products will behave overall. Tests using commercially available products rather than individual ingredients have shown that with the right combination of ingredients, comedogenic compounds can become less or even non-comedogenic.[10] Again, how often you use a product and how much of it you use for each application will affect the outcome. The purity of each ingredient also matters; one study tested cocoa butter samples from different commercial batches and discovered the severity of the comedogenic response differed for each.[4]
Other Factors to Consider
The FDA does not regulate the use of the word noncomedogenic; it does, however, condemn the use of dishonest or deceptive label statements.[11] There is no true standard used to determine whether an ingredient, let alone a product, is non-comedogenic on the face. Testing is either conducted with rabbits who have much more sensitive skin than humans. Or in the case of human testing, ingredients are applied liberally and at higher concentrations than typically found in topical products. Furthermore, the human testing is done on the back, which has fewer pores than the face and will not likely reflect how a product may react on the face.
The Bottom Line
The term “non-comedogenic” is not as clear-cut as it may seem and may be used more often to create a marketing advantage for a product. If you have acne-prone skin, a product advertised as non-comedogenic could still break you out. On the other hand, most products avoid the use of ingredients that have historically been found to be comedogenic. Even if they don’t, the presence of individual comedogenic ingredients does not mean that the overall product will be comedogenic. You are also likely to use a much smaller amount of product than is typically tested. If you’ve been checking your products to make sure they’re labeled as non-comedogenic, you should realize that this label may not be as informative as hoped and you’re better off expending your time and energy elsewhere. All products should be carefully tested on the face and discontinued if they cause a breakout, regardless of what it may say on the label.
