Comedogenic ingredients are ingredients that lead to clogged pores, called "comedones." It is thought that comedogenic ingredients stimulate the overproduction of skin cells inside a skin pore, and this leads to a pore blockage, and ensuing acne.1,3,5,6
The term comedogenic refers to a substance that causes comedones. Sometimes dermatologists use the term acnegenic in place of comedogenic, but both of these terms have the same meaning. Researchers first discovered that cosmetic products could cause acne in 1972 after investigating the continued appearance of comedones in adult women who regularly used facial cosmetics. The researchers called the condition “acne cosmetica,” and this initial discovery led to much more research regarding exactly which ingredients might be causing clogged pores.5
The term non-comedogenic refers to substances that should not cause clogged pores.
The discovery of acne cosmetica prompted manufacturers to develop cosmetic and skin care products that are more likely to be non-comedogenic.3Today, a host of skin care brands advertise their products as non-comedogenic. However, people who use products labeled as non-comedogenic should know that the FDA does not regulate this term. This means that although some manufacturers can support their claims with research and product testing, no regulatory agency requires them to do so in order to make comedogenicity claims about their products.
Formulating Non-comedogenic Products
Producing non-comedogenic skin care products and cosmetics is a challenge because most products contain many ingredients, and it is difficult to predict how each of those ingredients will interact with different people’s skin.5Product formulators try to make educated guesses about how comedogenic an ingredient might be based on its chemistry, such as how big the molecule is.6
Another tool that product formulators have is to simply avoid using ingredients that have been shown to be comedogenic in laboratory testing. The first list of results for the comedogenic potential of ingredients was published in a 1989 study in the Journal of the Society of Cosmetic Chemists:
“By taking these products apart, testing their ingredients, and putting them back together and retesting them, an extensive ingredient listing has been created. By studying this list, the cosmetic chemist can begin to be selective in developing formulas for less irritating and less comedogenic products.”6
This first list showing us the comedogenic potential of various ingredients published in 1989 was very important and eye-opening. However, even if individual ingredients are classified as non-comedogenic, it is possible that a combination of non-comedogenic ingredients interact and become comedogenic. To avoid this, the American Academy of Dermatology recommended in 1989 that manufacturers test products that contain three or more non-comedogenic ingredients, just to be sure that the combination of ingredients doesn't end up clogging pores.3
The Comedogenic Testing Process
The rabbit ear test and the human method are the two testing models that are usually used to determine if ingredients are comedogenic.
The rabbit ear test:
The rabbit ear test is the most common way of determining whether ingredients are comedogenic. In this test, a researcher exposes the inner ear of an albino rabbit to an ingredient, for example, an oil at 10% strength, and evaluates how the skin responds after a two-week period.
The major limitation of this test is that the skin of a rabbit’s ear is much more sensitive than human skin, and sometimes ingredients appear to be more comedogenic in the rabbit than they are in humans.6
The human method:
Researchers also perform comedogenic testing of product ingredients on human skin, partly due to opposition to animal testing in some countries. In this method, an absorbent patch is saturated with an ingredient and applied to a person’s back, and then evaluated after four weeks. Researchers will often test several ingredients at once in this manner.
Comedogenic testing in humans presents a few disadvantages. Researchers have not used the human method for as long as the rabbit ear test. While the method of the rabbit ear test has been standardized, the human method has not. Because of this, different researchers will often employ the human method in different ways, leading to inconsistent outcomes. Another disadvantage of this test is that it takes more time to obtain results than it does with the rabbit ear test.3
As we can see, both the rabbit ear test and the human method come with downsides. Comedogenicity testing, consequently, is an imperfect science.
The Bottom Line
Since the FDA does not regulate the claim "non-comedogenic" on cosmetic and skin care products, it is difficult to know how much testing the manufacturer actually performed, if any, when they came to this conclusion. Due to this unregulated environment, as well as limitations in scientific understanding and product testing procedures, consumers should be aware that some “non-comedogenic” products may still cause clogged pores and breakouts.
The best way to determine if a product might break you out is to look at the ingredient list and avoid using products that contain highly comedogenic ingredients within the first seven (7) ingredients listed on the label.