Comedogenic rating; what does it mean?

The comedogenic rating is found often in texts dealing with natural oils and cosmetics. The abstract of comedogenic rating is unknown to many, even it is a familiar word. I wanted to clarify the basics of comedogenic rating and what it really means. Is there a scientific proof backing up the comedogenic rating and its scale? Can a single number define an oil as good or bad?  Sometimes it’s just good to research things thoroughly. Read on to find out almost everything essential about the comedogenic rating.


What is the comedogenic rating?

Comedo is the scientific name for blackheads on the skin, hence the word comedogenic. Comedogenic rating refers to the classification of cosmetic ingredients that clog pores of the skin according to their clogging properties.

Comedogenic classification scale

The comedogenic rating is determined for oils and other cosmetic ingredients according to the scale below.

  • 0 = does not support pores at all
  • 1 = very low clogging
  • 2 = moderately low clogging
  • 3 = moderate occlusion
  • 4 = fairly high clogging
  • 5 = high clogging

Comedogenic rating is an old concept

The comedogenic rating started in the 1950s, when scientists started to study the risks posed to workers by certain industrial chemicals. Scientists took the job seriously and scientific research was launched.

Test animals were, of course, used for scientific research. For some unknown reasons, innocent rabbits were chosen. The name of the study was “The Rabbit Ear Model”. You can google that study. You will find a lot of information on the subject.

The skin of the rabbits’ ears was shaved and various chemical preparations were applied to the bare skin. The Rabbit Ear Model research was not originally intended to be used in the cosmetics industry. However, it found its way there in the 1970s. In 1979, the very famous dermatologist Albert Kligman published the first comedogenic rating of cosmetics, the “Comedogenic Scale”. In it, cosmetic oils and other ingredients were scored on a 0-5 scale according to clogging feature (0 = good, 5 = bad). Kligman based his classification on the above-mentioned study of rabbit ears published in the 1950s.

Real life experience did not support the study

Very soon after Kligman published his list of comedogenic cosmetic ingredients, the truth began to be revealed. Skilled beauticians introduced the scale in their work. They found that the scale was not true at all. The oils that should have clogged the pores did not do that, and vice versa. People react to different oils very individually. The famous dermatologist Kligman suffered a serious loss of prestige and reputation. The much-promoted scale didn’t work in practice.

The studies were performed in rabbits, not humans

The research work had not been done properly. How a rabbit ear reacts to a vegetable oil was supposed to tell us how the same vegetable oil works on our own skin!  We have all certainly noticed how we all are different, unique human beings having big differences on our individual skins. How rabbit skin could reliably serve as an experimental platform for comedogenic classification for humans.

It should also be remembered that rabbits are also individuals. That study gave an idea of ​​how a particular batch of oil affected the skin of a particular rabbit’s ear. If a particular oil has caused a blackhead in the ear of a particular rabbit, it cannot be assumed that the same would happen to a human. So, there are a lot of parameters. The number of parameters makes the experiment particularly unreliable.

There are differences in natural oils

Another problem in the study concerns the oils themselves. The composition of natural oils can vary very much. Natural oils consist of several different fatty acids as well as glycerol. Different oils have their own fatty acid composition, which depends not only on genetics but also on many other things such as

  • Growing location
  • Variety
  • The time of harvest
  • The weather
  • Is the oil hydrogenated.
  • Organic oils and cold pressed oils behave completely differently on the skin than refined and heated oils.

This means that you cannot just trust that a particular oil is right for your skin. You must first know the fatty acid content of that particular batch of oil. The quality of the oil must also be known well.

Of course, an indicative oleic acid profile can be defined for oils. For example, coconut oil has a completely different fatty acid profile than sunflower oil or olive oil.

I have published a fatty acid index of natural oils on my website. There you will find most of the known vegetable oils and their average fatty acid profiles. The comedogenic value of each oil is also mentioned there.

Use oils moderately


One fairly simple thing can be the cause of clogged skin. There is simply too much oil on the skin. The skin does not always need the oil at all, especially if the skin feels soft and smooth already. Do not unnecessarily clog the pores with oil. Allow skin to breathe freely.

When applying the oil on the skin, always apply it to moisturized skin. When applied to dry skin, the oil easily clogs the pores. While washing your face with water, dry lightly and immediately add a few drops of oil or moisturizer. You can also use effective moisturizing toners before applying oils to your face.

Cosmetic products can be surprising

Even if the cosmetic product contains substances that are not individually comedogenic, the combination can still clog the skin. This may surprise many cosmetic manufacturers and users. Often, finished products may contain a preservative or emulsifier that causes problems.

There are also many positive surprises. If you use highly comedogenic oil in rinse-off products, there will usually be no problems. Also in body products, many oils that clog the skin are not a problem.

The comedogenic scale does not indicate the suitability of the cosmetic product

The purpose of this article was to tell you that comedogenic scale of oils for skin care is not the key to happiness. It can give some information about oils but that is not the whole truth.

It is very unfortunate that comedogenic scale has spread widely and is very popular. On my website, a comedogenic value of oils is marked as well. I state the value only because it seems to interest quite many readers. However, I wanted to write this article to tell what can be found behind the comedogenic scale. Now you can decide for yourself whether you believe the scale or not.

Using Animals for testing is unethical

I am not in favour of using animals when testing cosmetics. Therefore, I would not like to emphasize the comedogenic rating ​​of oils in my texts either. The cosmetics industry has also not really wanted to use animal testing itself. In cosmetics, animal testing has largely been done to meet the requirements of the authorities, not for the manufacturers’ own needs. This rabbit ear study was also conducted on the initiative of the scientific world.

The use of rabbit ears to determine comedogenicity has been scientific at the time. At present, that study is no more science.

Focus on fatty acids

If you really want to find the right products for your skin, focus on the fatty acids in the oils. The different fatty acids in the oils affect the skin in different ways. By researching oils and comparing their fatty acid contents, you can find truly great oils for different purposes. There is such a huge variety of vegetable oils. No one will ever be able to try them all. Only by understanding the importance of different fatty acids will guide you through the oil jungle.

Consult a professional dermal therapist


If you really have acne or particularly impure skin, I highly recommend that you consult a qualified dermal therapist. Severe acne may also require a visit to a dermatologist. In any case, a qualified dermal therapist will be able to recommend a doctor’s consultation if necessary. Choose your dermal therapist with special care. Ask your friends for recommendations and read comments online and in magazines. A good dermal therapist is a must in skin care.

Acne and other skin problems are never treated with external treatment alone. Diet and indoor humidity as well as outdoor temperature are very important.

You can still follow the comedogenic scale of the oils if you wish. Now you know  more about oils and know how to find the best one for you.

Do you monitor the comedogenic values ​​of oils?

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