Are Comedogenic Ratings Reliable? What the Studies Show

Partly. Comedogenic ratings work as a rough screen: ingredients rated moderately to strongly comedogenic in rabbit ears have also induced comedones in human tests [3]. They work poorly as a prediction for a finished product or for your skin, because they come from isolated ingredients, shift with source and concentration, and have no standardized test behind them [2][7][9].

Key takeaways

1. Strong ratings have held up in human back tests. Weak or negative ratings are the more dependable signal [3][4].
2. A rating describes an ingredient on its own. A 2006 study found that finished products using comedogenic ingredients are not necessarily comedogenic [7].
3. The same ingredient can score differently by source, refinement and the vehicle it is mixed in [2].
4. Two case-control studies in real users point in different directions, so real-world evidence is mixed [12][13].
5. Use ratings to decide what to check first, then let your own skin settle it.

Do comedogenic ratings hold up? A five-question scorecard

How were the ratings built?

The idea began with Albert Kligman and Otto Mills in 1972. Half of the 25 facial creams they tested were mildly comedogenic in rabbit ears, and common ingredients such as lanolin, petrolatum, certain vegetable oils, butyl stearate, lauryl alcohol and oleic acid were too. Those materials were only weakly comedogenic compared with tars and chlorinated oils [1].

James Fulton's 1989 survey later graded hundreds of ingredients on a 0 to 5 scale [2]. For how those grades work, see What Does Comedogenic Mean?. For the grades themselves, see the Comedogenic Ingredients List.

Where do ratings hold up?

The best support comes from the 1982 human model. Mills and Kligman applied test substances under occlusion for one month to the upper backs of young men with large follicles, then lifted follicle contents with cyanoacrylate glue [3]. Substances that were moderately to strongly comedogenic in rabbit ears induced comedones in people. The rabbit model was more sensitive than the human one, and substances weakly comedogenic in rabbits were probably safe for human use, with the possible exception of acne-prone people [3].

Fulton's 1984 paper reached a similar view. He called the rabbit ear 'not an ideal animal model but the best we have' and said an ingredient that is negative in it is safe for acne-prone skin, while a strong positive should be avoided [4].

Concentration matters too. A review of the early data reported that Kligman and Mills found most vegetable oils had some degree of comedogenicity, usually low, and that all were inactivated when diluted to 25% in mineral oil [5].

So ratings work best as a negative screen. A low grade is more reassuring than a high grade is alarming.

Where do ratings break down?

1. The rabbit ear overreacts. Fulton himself called it extremely sensitive and said not everything that irritates it will irritate human skin [2]. Later studies pointed out that it overreacts to comedogenic materials [6].
2. A formula is not its ingredients. In a 2006 study, six people wore patches of finished products on their upper backs for four weeks. The authors concluded that finished products using comedogenic ingredients are not necessarily comedogenic. The sample was small and only a finite number of products were tested [7].
3. Source and vehicle change the grade. In Fulton's data, lanolin alcohol, jojoba oil and beeswax each graded 0 to 2 depending on raw material. A red pigment graded 3 in mineral oil and 0 in PEG 400 [2].
4. Where you test matters. A study of 66 women found that comedones on the face and body correlate only in some regions, and recommended testing both on the back and directly on the face [6]. In-use trials on the face, where volunteers use a product for 4 to 6 weeks, are described as the gold standard, but they cost more than back tests [8].
5. There is no standard. A 2018 JAMA Dermatology letter said reliable, standardized testing behind non-comedogenic claims was still lacking [9]. A 2018 systematic review found that terms such as non-comedogenic and oil-free are not regulated by any governing body [10]. A 2025 review makes the same point about regulatory gaps [11].

What happens in real life?

Two case-control studies test the idea outside the lab, and they do not agree neatly.

A 2013 study compared 910 post-adolescent patients with acne against matched controls. As overall cosmetic exposure rose, the odds of acne fell: odds ratios were 0.679, 0.355 and 0.307 across three rising exposure bands. Some individual cosmetics, though, had odds ratios above 1 [12].

A 2025 study of 151 participants found that facial cleansers, foundation and powders were linked to a higher risk of acne. Facial cleansers containing comedogenic ingredients were an independent risk factor (odds ratio 2.49, 95% confidence interval 1.23 to 4.90) [13]. That study was small and relied on self-reported questionnaires, so it shows an association, not proof of cause.

Together they suggest that using cosmetics is not the problem. Specific products and ingredients may be.

How reliable is reliable enough?

To get more from a rating:

1. Check position and product type. A flagged ingredient high on the list of a leave-on product matters more than one near the end of a cleanser.
2. Look at families, not single numbers. If several ingredients from a high-scoring family appear, that is a stronger signal than one borderline grade.
3. Test on your own skin. Add one product at a time and give it several weeks, since in-use trials run four to six weeks [8].

To do the first two steps faster, paste an ingredient list into the Klenzera scanner and see which ingredients to look at first.

Frequently asked questions

Are comedogenic ratings scientifically valid?

They are valid as a rough screen, especially for strongly rated ingredients, but not as a precise prediction for a finished product [3][7].

Why do websites give different numbers for the same ingredient?

Sources differ in testing method, concentration, refinement and vehicle [2].

Does non-comedogenic mean a product was tested?

Not necessarily. The term is not regulated, so a brand can use it with or without testing [10].

Should I avoid everything rated 2 or higher?

No. Fulton read 2 to 3 as borderline and 4 to 5 as positive [2], and finished products can behave differently from their ingredients [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

Comedogenic ratings are a reasonable first filter and a poor final answer. Trust a low grade more than a high one, and trust your own skin most of all.

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: What Does Comedogenic Mean? | Comedogenic Ingredients List

References

1. Kligman AM, Mills OH Jr. Acne cosmetica. Arch Dermatol. 1972;106(6):843-850.
2. Fulton JE Jr. Comedogenicity and irritancy of commonly used ingredients in skin care products. J Soc Cosmet Chem. 1989;40:321-333.
3. Mills OH Jr, Kligman AM. A human model for assessing comedogenic substances. Arch Dermatol. 1982;118(11):903-905. PMID 7138047
4. Fulton JE Jr, Pay SR, Fulton JE 3rd. Comedogenicity of current therapeutic products, cosmetics, and ingredients in the rabbit ear. J Am Acad Dermatol. 1984;10(1):96-105. doi:10.1016/s0190-9622(84)80050-x
5. Morris WE, Kwan SC. Use of the rabbit ear model in evaluating the comedogenic potential of cosmetic ingredients. J Soc Cosmet Chem. 1983;34:215-225.
6. Analysis of comedone, sebum and porphyrin on the face and body for comedogenicity assay. Skin Res Technol. 2016;22(2):164-169. doi:10.1111/srt.12244
7. 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
8. Caswell M. Non-comedogenic and non-acnegenic claim substantiation. J Cosmet Sci. 2017;68(4).
9. 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
10. 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
11. Comedogenicity in cosmeceuticals: a review of clinical relevance, regulatory gaps, and future directions. JAAD Reviews. 2025.
12. Acne cosmetica revisited: a case-control study shows a dose-dependent inverse association between overall cosmetic use and post-adolescent acne. Dermatology. 2013;226(4):337-341. doi:10.1159/000350936
13. Choi K, Liu H, et al. A case-control study exploring the association between cosmetic use and acne risk: implications for prevention and clinical practice. Clin Cosmet Investig Dermatol. 2025.