Comedogenicity refers to the potential of an ingredient to cause acne when applied to the skin.
Comedogenicity in skincare and cosmetics has been researched for years, but it has only recently become popular as consumers become more skincare-savvy.
Skincare enthusiasts and specialists scrutinize ingredient lists for labels like “noncomedogenic” or “non-clogging,” hopeful that it will not aggravate acne-prone and sensitized skin.
However, what exactly does this label mean? Does these claims have validity to them?
As we examine comedogenicity in more detail, we find that it is a complex and multifaceted topic.
How Do Comedogenic Ingredients Cause Acne?
Comedogenic ingredients can clog pores and cause acne.
It facilitates a keratin buildup inside hair follicles—a process known as follicular hyperkeratosis.
This process leads to comedones and clogged pores. Breakouts can happen quickly or over a long time as the skin reacts to a highly comedogenic product.
Acne Cosmetica is a moderate form of comedonal acne caused by or aggravated by cosmetic or skincare products.
Various factors can influence a product's comedogenicity:
- Concentration – “The dose makes the poison.” The high comedogenicity rating of certain ingredients in their pure form can drop down to non-existent when diluted. E.g., Olive oil is moderately comedogenic at grade 2 but is reduced when mixed with mineral oil and diluted down to 25% concentrations
- Personal skin chemistry – Oily and acne-prone skin develops comedones quicker than dry and non-sensitive skin.
- Product formulation – E.g., A pair of highly comedogenic ingredients is likely unsafe for acne-prone skin. The same ingredients with a significantly lower dose in a formula will not cause the same problem, except for very sensitive skin.
Because a person's unique skin chemistry influences an ingredient's comedogenicity, it varies significantly between people.
You may not react to a product, but another can have severely congested pores in several days.
The sebum produced by our skin is comedogenic by nature.
Even if people predisposed to congestion avoid all potentially comedogenic products, there's no guarantee they will not experience acne cosmetica.
So how can you tell if certain ingredients contribute to clogged pores or breakouts?
The rabbit ear test was the gold standard for determining comedogenicity for many years.
This test, which was developed in the 1950s, was originally used to evaluate the hazards of industrial chemicals. In the 1970s, it was used in cosmetics.
Rabbit ears are much more sensitive to comedogenic substances and respond much faster than human skin.
Follicular hyperkeratosis, “follicular plugging,” would appear within weeks rather than months.
James Fulton, MD, and Albert Kligman, MD, Ph.D., are credited for popularizing the rabbit ear test in cosmetic research and coining the phrase “acne cosmetica”—which is acne induced by comedogenic cosmetics.
Kligman and Fulton performed cosmetic rabbit ear testing by applying chemicals to the rabbit's inner ears.
After a few weeks, follicular keratosis was evaluated microscopically and visually.
The first list of comedogenic ingredients was divided into 12 categories:
- fatty acids
- alcohols and sugars
- vitamins and herbs
- miscellaneous ingredients
The ingredients were ranked on a scale of 0 to 5.
- Comedogenic rating 4 – 5 – caused a significant increase in the occurrence of large comedones and follicular keratosis throughout the ear. These are reproducible results and are considered very comedogenic.
- Comedogenic rating 2 – 3 – only moderately increased follicular keratosis
- Comedogenic rating 0 – 1 – displayed no substantial increase and is considered as non-comedogenic
Those with acne-prone or oily skin should avoid high concentrations of ingredients with high comedogenic ratings.
Human participants are now used in comedogenic testing as consumers now frown upon animal testing.
These tests are usually performed in third-party laboratories, with each lab performing different tests.
Patch applications are typically administered to 10-30 participants and tested against a known comedogenic ingredient. An untreated site is tested as well for the negative control.
The back is a frequently chosen site, but this depends on the lab.
(Note that facial skin is ideal, but there is no viable way to test against every skin type and condition. It also opens the test to additional variables.)
A surface biopsy is performed at the end of the testing phase, and the cells are then examined under magnification.
Testing typically lasts four to eight weeks. The testing conditions can also be tailored to the manufacturer.
Validity of Claims Regarding Ingredient Comedogenicity
The main problem with the standard method of evaluating an ingredient's comedogenicity is that the skin of the back is unreliable.
The body's skin responds differently to facial skin.
The testing time is insufficient as well.
Several factors contribute to discrepancies in comedogenic ingredient lists.
First, the concentration of the ingredient inside the formula is key.
The product formula is more than the sum of its parts. Combinations of ingredients can alter a comedogenic component into a non-comedogenic element and vice versa.
Second, how an ingredient is extracted and processed is also important.
An ingredient's refinement, hydrogenation, or fractionation can significantly alter its comedogenicity ranking.
Third, the raw material's origin can influence its rating.
Unfortunately, reading an ingredient label will not reveal these variables.
The issue is further complicated by Food and Drug Administration guidelines in the United States.
According to the FDA, a comedogenic ingredient is a substance known to facilitate clogged pores.
However, the FDA does not specify a list of ingredients that must be excluded for a product to be labeled “non-comedogenic.”
So, in the end, any business can claim that its product is non-comedogenic and still comply with FDA guidelines.
Furthermore, no standardized testing or regulatory agencies detect claim misuse.
Even if the industry attempted standardization, it would be a difficult and expensive task.
To date, third-party testing of a complete formula on human skin is the best way to determine whether or not a product is comedogenic.
It is also the only way to legally back up claims like “non-comedogenic,” “unclogs pores,” or “reduces the appearance of blackheads.”
However, third-party testing is costly, and because there is little to no regulation over the term usage, very few cosmetic companies go the extra mile.
This is especially problematic with new ingredients without prior rabbit ear comedogenic studies.
Consumers are forced to sift through the literature, searching for studies about the ingredients or simply relying on anecdotal evidence.
Comedogenic ingredient listings can serve as guidelines; however, it should be noted that only a few ingredients—in all of their forms—have consistently demonstrated comedogenicity in scientific studies.
Table 1: Comedogenic Ingredients
This table lists highly comedogenic ingredients.
- Acetylated lanolin
- Butyl stearate
- Cetearyl alcohol and
- Cetyl acetate
- Coal tar
- Cocoa butter
- Coconut oil
- Ethylhexyl palmitate
- Glyceryl-3 diisostearate
- Isocetyl alcohol
- Isopropyl isostearate
- Isopropyl linolate
- Isopropyl myristate
- Isopropyl palmitate
- Isostearic acid
- Linoleic acid
- Lauric acid
- Linseed oil
- Myreth-3 myristate
- Myristyl lactate
- Myristyl myristate
- Octyl palmitate
- Oleic acid
- Oleyl alcohol
- Olive oil
- Peg-16 lanolin
- Stearyl heptanoate
Table 2: Non-Comedogenic Ingredients
This table shows ingredients that are frequently mislabeled as comedogenic but are not.
- Butylene glycol
- Emulsifying wax National Formulary (NF)
- Iron oxides
- Isopropyl alcohol
- Propylene glycol
- Specially denatured (SD) alcohol
To avoid contentious ingredients, the lists are not exhaustive but an abbreviated consensus from several well-known records.
Choosing the Right Products
Although comedogenicity is not an exact science, you can take steps to make suitable product choices.
- Learn about the theory of comedogenicity. Understand that even if you love a particular product, it may not be the best choice for your acne-prone skin if it contains comedogenic ingredients.
- Check the ingredient lists. It's worth mentioning that many companies place the ingredient label on the outer package rather than directly on the product, so you may need to look up the complete ingredient list online or contact the manufacturer directly.
- Be selective about your ingredients. Components with similar names are not the same. Isocetyl alcohol differs from isopropyl alcohol; steareth-2 differs from steareth-10; caproic acid differs from capric acid, and squalane differs from squalene. Keep a list.
- Remember that comedogenic ingredients include emulsifiers, thickeners, surfactants, waxes, and oils. For example, “oil-free” does not imply “noncomedogenic.” Although some oils are comedogenic, others are not, and some are beneficial to acne-prone skin.
- Look for brands that have independent third-party comedogenic testing performed by reputable labs. This may not be obvious from the label; if so, contact the manufacturers directly. Don't be afraid to inquire about their research findings. If third-party testing is unavailable, request the information that led them to conclude that their product is noncomedogenic.
RELATED: NON-COMEDOGENIC SKINCARE
Take Extra Precautions
A product containing a comedogenic ingredient is not necessarily bad; it may simply not be the best choice for someone who struggles with clogged pores or acne. It could be a fantastic product for those with drier skin and smaller pores.
Although everyone's skin reacts differently, it's best to avoid known comedogenic ingredients if you have acne-prone skin. With so many options on the market today, it's easy to take extra precautions.
RELATED: NON-COMEDOGENIC MAKEUP
- Draelos, Zoe Diana, and Joseph C. DiNardo. “A re-evaluation of the comedogenicity concept.” Journal of the American Academy of Dermatology 54.3 (2006): 507-512.
- Fulton, J. E. “Comedogenicity and irritancy of commonly used ingredients in skin care products.” J. Soc. Cosmet. Chem 40 (1989): 321-333.
- Fulton Jr, J. E., et al. “Non-comedogenic cosmetics.” Cutis 17.2 (1976): 344-5.
- Fulton Jr, James E., Stephen R. Pay, and James E. Fulton III. “Comedogenicity of current therapeutic products, cosmetics, and ingredients in the rabbit ear.” Journal of the American Academy of Dermatology 10.1 (1984): 96-105.
- Ghani, Hira, et al. “An Investigation of Makeup Ingredients and their Effects on Acne Cosmetica with Dermatologic Practice Recommendations.” SKIN The Journal of Cutaneous Medicine 5.5 (2021): 474-481.
- Kligman, Albert M., and Otto H. Mills. “Acne cosmetics.” Archives of dermatology 106.6 (1972): 843-850.
- Kligman, A. M., and TILLIE KWONG. “An improved rabbit ear model for assessing comedogenic substances.” British Journal of Dermatology 100.6 (1979): 699-702.
- Mills, Otto H., and Albert M. Kligman. “A human model for assessing comedogenic substances.” Archives of Dermatology 118.11 (1982): 903-905.
- Morris, William E., and Shih Chao Kwan. “Use of the rabbit ear model in evaluating the comedogenic potential of cosmetic ingredients.” J. Soc. Cosmet. Chem. 1983.