Ever broken out from a non-comedogenic product before?
By their very definition, they are technically not supposed to clog pores. So why and how did the opposite happen?
The origins of comedogenicity
'Comedogenicity' is the ability for something to cause comedones or clogged pores. This concept came about in the 1970s to explain how acne can be caused by the application of certain cosmetic products.
The original study involved applying different ingredients on rabbits' ears and see if they caused comedones. The comedogenicity of the ingredients were scored on a scale of 0-5. A non-comedogenic ingredient rated 0 whilst a highly comedogenic one rated 5.
Validity of comedogenicity ratings
Later, it was found that results of the rabbit ear tests were not applicable to human skin and that individual ingredients’ comedogenicity ratings alone do not reliably predict products’ comedogenicity. Hence these tests became obsolete over time.
Modern comedogenicity tests
Today, comedogenicity tests are done on human volunteers using the finished product.
However, like the rabbit ear test, it also has drawbacks mostly because there is no standardised or consistent way of these testings. Therefore, human comedogenicity test design and result interpretation can be both inconsistent and inconclusive. So really, there is simply no way of accurately judging comedogenicity from such tests.
What to look out for instead
Since the 'non-comedogenic' claim is not definitive, what can we do to determine if a product will cause blocked pores?
- Product consistency
Usually, the thicker the product, the more likely it will block pores. If you are prone to clogged pores, choose lightweight products that spread and absorb quickly instead of thick, tenacious creams.
- Amount and type of oils
Generally, the higher the oil content, the more likely it will cause comedones. The type of oil also matters. Plant oils (especially olive, almond, coconut oils and cocoa butter) have a higher propensity to clog pores. If you have are particularly acne-prone, it is better to avoid plant oils entirely.
- Length of time of skin contact
Product that stay on skin for longer has a higher chance to cause clogged pores. Choosing a moisturiser generally needs more careful consideration than a cleanser. However, some cleansers (balm, cream or oil-based) do not actually doesn't wash off completely. So the same degree of caution will apply in those cases.
At the end of the day, 'non-comedogenicity' as a measure may be reassuring but not a certainty. We can make a good guess from observing and feeling the product, but the only sure way to know is to use it.
Kligman and Mills, Acne Cosmetica, Arch Dermatol. 1972;106(6):843-850. doi:10 1001/ archderm. 1972.01620150029011
Morris and Kwan, Use of the rabbit ear model in evaluating the comedogenic potential of cosmetic ingredients, j. Soc. Cosmet. Chem., 34, 215-225 (August 1983)
Kligman, Petrolalum is not comedogenic in rabbits or humans: A critical reappraisal of the rabbit ear assay and the concept of "acne cosmetica", J. Soc. Cosmet. Chem., 47, 41-48 (January/February 1996)
Fulton, Comedogenicity and irritancy of commonly used ingredients in skin care products, J. Soc. Cosmet. Chem., 40, 321-333 (November/December 1989)