Comedogenic means an ingredient or product may block pores and lead to comedones, the blackheads and whiteheads behind many breakouts. Ingredients are often rated on a 0 to 5 scale, where 0 means unlikely to clog pores and 5 means very likely. The scale is a useful screening tool, but it is not a prediction.
Key takeaways
- Comedogenic describes how likely an ingredient or product is to block pores and form comedones.
- The familiar 0 to 5 ratings grew out of rabbit-ear testing in the 1970s and 1980s, not from large trials on human faces.
- A 2006 study found that finished products made with comedogenic ingredients are not necessarily comedogenic.
- 'Non-comedogenic' on a label is a marketing term with no regulated meaning.
- Use ratings to shortlist products, then judge each product on your own skin.
What does comedogenic mean?
Comedogenic describes a substance that may encourage comedones. A comedone is a clogged hair follicle, either open (a blackhead) or closed (a whitehead). A non-comedogenic product is one its maker says is unlikely to clog pores.
That last definition has a catch. A 2018 systematic review found that terms like non-comedogenic and oil-free are not regulated by any governing body [6]. Any brand can print them.
Comedogenic is also not the same as irritating. Fulton's 1989 paper, one of the most cited ingredient references, scored comedogenicity and irritancy separately [3].
Where did the comedogenic scale come from?
Dermatologists Albert Kligman and Otto Mills introduced the term 'acne cosmetica' in 1972 to link cosmetic ingredients with comedones in young women [1][2]. Fulton's 1989 paper recounts their survey: about one third of adult women at a university acne clinic had low-grade, persistent acne on the cheeks, made up of closed comedones [3].
To rate ingredients, researchers used the rabbit ear model, which applies a substance to a rabbit's ear and checks the follicles for plugging. Early grading used a 0 to 3 scale [2]. Ingredient lists on a 0 to 5 scale now circulate widely, and Fulton's 1989 paper is among the sources they most often cite [3].
About ten years later, Mills and Kligman tested the same chemicals on people. The human results did not line up with the rabbit results [2].
| Year | Milestone | What it tells us |
| 1972 | Kligman and Mills describe acne cosmetica | A link between cosmetics and comedones is proposed [1][2] |
| 1982 | Human model tests the same chemicals | Results differ from rabbit ears [2] |
| 1989 | Fulton reports comedogenicity and irritancy of common ingredients | Frequently cited source for 0 to 5 lists [3] |
| 2006 | Draelos and DiNardo test finished products | Comedogenic ingredients do not guarantee a comedogenic product [4] |
| 2018 | JAMA Dermatology research letter | Standardized, validated testing was still lacking [5] |
How is comedogenicity tested?
Three approaches are used, and they do not always agree.
- Rabbit ear model. An ingredient is applied to a rabbit's ear. It is inexpensive, but the authors of a 2018 JAMA Dermatology letter say it does not offer an ideal assessment of human comedogenic potential [5].
- Human back patch test. In the 2006 study, patches with 0.2 to 0.5 mL of finished product were applied to the upper back three times a week for four weeks. Cyanoacrylate biopsies then counted follicles and microcomedones [4].
- In-use trial. Volunteers use a product on their faces for several weeks, and a dermatologist counts lesions [7].
What the research says about the limits of the scale
Three findings matter most when you read a rating.
- A rating describes an ingredient, not your moisturizer. In the 2006 study, six people used finished products on their backs for four weeks. The authors concluded that finished products using comedogenic ingredients are not necessarily comedogenic. The study was small and tested a limited number of products, so treat it as a caution, not a rule [4].
- Formulas are a black box. Added inactive and proprietary ingredients mean the comedogenicity of a final formulation is often unknown [5].
- Testing is not standardized. The 2018 letter noted that, 46 years after acne cosmetica was described, standardized and reliable testing behind non-comedogenic labels was still lacking [5].
Ratings are also often based on the undiluted ingredient, and the same ingredient can carry a range, such as 0 to 2, depending on the study or whether an oil is refined [8].
How to read a comedogenic rating
This is a rule of thumb, not a published threshold. Ratings differ between sources.
| Rating | Practical reading |
| 0 to 1 | Low concern. Unlikely to be the problem on its own |
| 2 to 3 | Worth a look. Matters most when it sits high on the list of a leave-on product |
| 4 to 5 | Higher concern. Consider a patch test or an alternative if you are prone to clogged pores |
Three questions to ask before you worry about a rating
- Where is it on the ingredient list? Lists generally run from largest amount to smallest, so an ingredient near the top is present in a more meaningful amount than one near the end.
- Is the product leave-on or rinse-off? A cleanser touches your skin briefly. A moisturizer or foundation stays on for hours.
- How strong is the evidence behind the rating? A single old animal test deserves less weight than repeated human data.
Check your own products with Klenzera
Klenzera's scanner checks a product's ingredient list against comedogenic ratings from published research, so you can see which ingredients to look at first. Scan a product or paste an ingredient list, shortlist the ones that look better for your skin, then add them to your routine one at a time.
Frequently asked questions
Does comedogenic mean a product will give me acne?
No. It means an ingredient may contribute to clogged pores in some people. Your skin, the full formula and your routine all play a part [4][5].
Is 'non-comedogenic' regulated?
A 2018 systematic review found it is not regulated by any governing body [6].
Why do lists rate the same ingredient differently?
Sources differ in testing method, concentration and whether an ingredient is refined [8].
How long should I test a new product?
Introduce one product at a time and give it several weeks. In-use trials typically run four to six weeks [7].
When should I see a dermatologist?
If breakouts are painful, cystic, scarring, persistent or suddenly worse, or if you suspect an allergic reaction, talk to a dermatologist or doctor.
The bottom line
The comedogenic scale is a starting point, not a verdict. Use it to decide which products deserve a closer look, then let your own skin make the final call.
This article is for educational and informational purposes only and is not dermatological diagnosis, medical treatment, or clinical advice. Talk to a licensed dermatologist about medical concerns.
Related reading: Browse all Klenzera articles
References
- Kligman AM, Mills OH Jr. Acne cosmetica. Arch Dermatol. 1972;106(6):843-850.
- Mills OH Jr, Kligman AM. Human model for assessing comedogenic substances. Arch Dermatol. 1982;118:903-905. Early rabbit-ear grading and the human comparison are summarized in Acne Management: A Role for Cosmetics? Acne & Rosacea Review, HMP Global Learning Network. hmpgloballearningnetwork.com/site/thederm/article/8216
- Fulton JE. Comedogenicity and irritancy of commonly used ingredients in skin care products. J Soc Cosmet Chem. 1989;40:321-333.
- Draelos ZD, DiNardo JC. A re-evaluation of the comedogenicity concept. J Am Acad Dermatol. 2006;54(3):507-512. doi:10.1016/j.jaad.2005.11.1058
- Maarouf M, Saberian C, Shi VY. Myths, truths, and clinical relevance of comedogenicity product labeling. JAMA Dermatol. 2018;154(10):1131-1132. doi:10.1001/jamadermatol.2018.1741
- Clinical utility of marketing terms used for over-the-counter dermatologic products. J Dermatolog Treat. 2018;29(8):841-845. doi:10.1080/09546634.2018.1467540
- Caswell M. Non-comedogenic and non-acnegenic claim substantiation. J Cosmet Sci. 2017;68(4).
- INCIDecoder. On comedogenic and irritancy ratings. incidecoder.com/comedogenic-rating