WTF Does Comedogenic Mean?
If you are acne-prone or skincare obsessed then you’ve probably heard about comedogenic products or ingredients. Acne experts and licensed estheticians alike are known to point their clients to online "ingredient checkers” to make sure the products they are using are acne-safe. But what if I told you the individual ingredient didn’t matter at all, actually?
Shocking, I know. Especially coming from one of the first ambassadors for the largest professional skincare line tailored to acne clients. But here’s the thing: you’re too focused on what one ingredient may or may not do and as a result foregoing complete formulations that will actually help heal your skin. The comedogenic scale and its strongest proponents have basically created an environment where we’re trying to force the client to understand complex chemistry every time they visit their local drugstore or beauty shop.
And honestly we should just stop.
Because our clients are not chemists (and most of us aren’t either)! And, in 2025, we aren’t even sure what comedogenic really means.
Origins and Development
The concept of comedogenicity has a fascinating yet problematic history. The comedogenic scale—a 0-5 rating system for ingredients' potential to clog pores—originated in the 1950s as an industrial safety measure rather than a cosmetic standard. Dr. Albert Kligman developed the rabbit ear model (REM) to assess risks posed to workers handling certain industrial chemicals. This method involved applying substances to rabbit ears and observing whether blackheads (comedones) formed.
The approach to comedogenicity testing evolved over time:
1950s-1970s: Initial rabbit ear model developed for industrial chemical assessment
1982: Testing shifted to humans, specifically male prisoners, with substances applied to their backs rather than their faces—still problematic as back skin differs significantly from facial skin.
1989: The American Academy of Dermatology (AAD) stated that "if the rabbit ear test does not show evidence of comedogenesis, the test material under consideration is unlikely to be comedogenic in human skin." This provided limited guidance but no comprehensive assessment method.
Despite its widespread use today, the comedogenic scale lacks official standardization or FDA regulation. There is no FDA definition or regulation for non-comedogenic claims on products, allowing manufacturers considerable freedom in how they use this terminology.
Scientific Evidence: The Formulation Effect
Modern research has revealed major flaws in the comedogenic scale's premise that individual ingredient ratings reliably predict a finished product's effect on skin. Multiple studies demonstrate that formulation factors significantly alter an ingredient's comedogenic potential:
Concentration Effects
Research shows that known comedogenic substances proved to be non-comedogenic at lower concentrations. For example, isopropyl isostearate has a comedogenic ranking of 4 when applied at 100%, which drops to 2-3 at 50% concentration, and further to 1-2 when used at just 5%. This demonstrates a clear dose-response relationship that the traditional scale fails to account for.
Vehicle and Product Type
The vehicle (carrier system) and product type significantly influence an ingredient's comedogenic potential. An ingredient in a powder product or in an evaporating vehicle like alcohol or water may be non-comedogenic, while the same ingredient in an oil-based vehicle may become comedogenic. To make things simpler, it is rare that a water-based serum or cleanser will be comedogenic. Creams, lotions, masks, and even our sunscreens have a higher potential for being comedogenic than others.
Rinse-off vs. Leave-on Products
Product application methods also matter considerably. Rinse-off products containing potentially comedogenic ingredients often don't cause problems because they have insufficient contact time with the skin. For example, cleansing oils containing comedogenic emollients like isopropyl palmitate actually help remove sebum, SPF products, and waterproof makeup that might otherwise clog pores.
Formulation Interactions
A 2006 re-evaluation study published in the Journal of the American Academy of Dermatology reached the critical conclusion that "finished products using comedogenic ingredients are not necessarily comedogenic." This research confirms that ingredients interact within formulations in ways that can mitigate or amplify their individual properties.
Limitations of the Comedogenic Scale
The comedogenic scale faces several fundamental limitations that affect its reliability:
Testing Methodology Issues
Both testing models have significant flaws: the rabbit ear model doesn't represent human skin responses, while the human testing model typically uses skin on the back (not face), involves occlusion (covering the product with a patch), and uses undiluted or highly concentrated ingredients under extended application times—conditions that don't reflect normal product use.
Individual Variability
Comedogenicity is essentially a catch-all phrase, as different oils affect individuals differently. Some people may find ingredients like cocoa butter or olive oil cause congestion, while others experience no adverse effects when using the same products. A tiny caveat I’d make to this is that the probability of an ingredient to cause congestion may also depend on where it is applied on the body. For example, applying shea butter to the face may directly result in congestion for some but applying to the arms or legs won’t.
Small Sample Sizes
Human testing studies typically use small sample sizes (up to 10 subjects), which don't provide adequate statistical power to extrapolate results to the general population. There also isn’t enough variation in where the human subjects come from. Environmental factors could also be a greater contributing factor in comedogenicity than we realize.
Inconsistent Ratings
Many websites and sources that share comedogenic rating charts provide no substantiation or study references for their information, raising questions about their accuracy. Ratings for the same ingredient often vary between different sources.
Status of Updates to the Comedogenic Scale
Despite significant advancements in dermatological research, there has been no comprehensive, standardized update to the comedogenic scale in recent years. According to multiple sources, the ratings most commonly used today still largely derive from studies conducted in the 1970s and 1980s, particularly the work of Dr. Albert Kligman and Dr. James Fulton (who published a significant list in 1989).
A 2018 article in JAMA Dermatology addressed "Myths, Truths, and Clinical Relevance of Comedogenicity Product Labeling," highlighting the ongoing limitations of the scale but not introducing a standardized replacement. And there really hasn’t been any new updates regarding the comedogenic scale since 1989. Basically the comedogenic scale as we know it has gotten a master’s degree, a house, and has probably been married and divorced by now.
The most significant scientific advances have been in understanding the limitations of the scale rather than updating it comprehensively. For example, the same 2006 re-evaluation study published in the Journal of the American Academy of Dermatology demonstrated that "finished products using comedogenic ingredients are not necessarily comedogenic," but did not establish a new standardized rating system.
Individual studies have tested specific ingredients or formulations, such as a 2021 safety assessment on comedogenicity of dermatological products containing d-alpha tocopheryl acetate, but these haven't led to a systematic overhaul of the comedogenic rating system itself.
Modern Understanding: Better Approaches
Rather than relying solely on the traditional comedogenic scale, experts now recommend more nuanced approaches. Instead of comedogenic rankings, guides based on fatty acid percentages may be more helpful in determining an ingredient's potential for skin disruption. For acne-prone skin, ingredients high in stearic and palmitic fatty acids (which have high melting points and don't absorb well at skin temperature) may be problematic.
Ratings should be viewed as guidelines rather than the law. Everyone's skin reacts differently, and some people can use ingredients with ratings of 4 without issue. The most reliable approach is to try a sample, use the product as directed, and observe how your skin responds—preferably changing only one product at a time in your skincare routine.
Lastly, evaluating a product's complete formulation rather than fixating on individual ingredients provides a more accurate picture of its potential effects. For example, surfactants in a cleansing oil can essentially nullify the comedogenic effects of emollients by enhancing rinse-off.
Conclusion
Don’t fall for fear-mongering and don’t try to be an ingredient detective. Those ingredient checkers and lengthy lists of products you can and can’t use don’t really mean much if the person who made it can’t tell you about the type of product formulation you’d want to steer clear from.
The comedogenic scale, while a useful starting point for those with acne-prone skin, should be viewed with careful consideration of its limitations. Formulation matters significantly, often more than individual ingredient ratings. Concentration, vehicle type, application method, and individual skin differences all influence how a product will affect your skin. For manufacturers, this research suggests that labeling products "non-comedogenic" should ideally be backed by testing of the finished formulation rather than relying solely on ingredient ratings.
As skincare science advances, we may eventually see more accurate, standardized testing methods that provide better guidance. Until then, the best approach combines the available science with careful personal observation. And if you’re looking for an esthetician that can thoughtfully explain why your current product formulation might be comedogenic for you (or why it sucks), then you know where to find me.
