Skincare with Friends Ep 81: Do We Need to Worry About Comedogenic Ingredients?

This concept is controversial, I’ll get on to why in a mo. You might have seen the term “Non Comedogenic” written on products and comedogenicity scores in sites like Skincharisma and Cosdna, warning us of ingredients products that might block our pores. We discussed blocked pores in our last episode- How to get Rid of Blackheads, head there for good product recommendations.

There is a score from 0-5 that is given to ingredients that give a measure of how likely the ingredient is to cause blocked pores, microcomedones and folliculiitis. 

This is fantastic knowledge for the acne sufferers. Avoid this highly comedogenic ingredient and you will be safe from product induced spots aka Acne Cosmetica. But sadly things are not so simple. 

One of the most frustrating parts of acne I find, is not knowing the cause. When you get a sudden outbreak, it’s so hard to figure out the why. It could be time of the month, irritation from a new acid (aka purging) or it could be that something just doesn’t agree with your skin and it’s always going to be a trigger. You might want to look to the research done on comedogenicity to get some clues as to whether your new moisturiser or whatnot contains something known to cause spots.

Let us find out if comedogenic ratings do what they are supposed to do and how to interpret them.

What Does “Non Comedogenic” Mean?

Basically “Comedo” is the science word for blackheads and noncomedogenic means “doesn’t cause blackheads”.

For brands to display “Non Comedogenic” which you might have seen displayed on product labels, they just have to avoid the ingredients which have flagged as highly comedogenic, the product itself will not have been tested for comedogenicity. The rabbit tests are, thank god, not allowed anymore and the human tests are too expensive and time consuming. There term “Non Comedogenic” is not regulated and anyone can display it on their product. The brand will be basing the claim on these rabbit studies rather than any experiments they will have done themselves.

What Are the Comedogenicty Experiments?

The experiments that test for comedogenicity are not very specific to real life situations. There have been numerous studies examining the comedogenicity of particular  ingredients most of which involve rabbit ears. 

The first Rabbit Ear Assays were performed by Kligman and Mills in 1972, this is what happened to the poor things-

They used a minimum of 3 rabbits for each substance and apply whatever they were testing at around 10% concentration just next to the rabbit’s earhole once a day 5-7 times a week for 2 weeks. They then look at the test sites under the microscope and compare it with the untreated control ear. They asses the amount of keratin impacted into the rabbits pores and give it a grade from 0-3 or 0-4.

“Studies comparing REA with human tests have indicated that the results are in correspondence but REA is far more sensitive. Thus, substances scoring 0 in REA are safe for humans. Those scoring 1 are most unlikely to be comedogenic, while substances scoring 2 or 3 are possibly comedogenic. 

However, there has been a lot of criticism on REA.

“Sometimes the results are conflicting, even under the same experimental conditions. Factors such as concentration, physical state, solvency and vehicle must be taken into account. In conclusion, REA is a useful method to establish comedogenicity but we reserve judgement on its prophetic value”

Katoulis et al, 1996

If the ingredient flags as comedogenic then the scientists test it out on humans. The same dudes Kligman and Mills came up with another technique in 1982- “The test material was applied under occlusion to the upper back of young adult men with prominent follicular orifices, 3 times/week for 4 weeks. Four test areas were used, with one of them serving as untreated control. This assay is not a substitute for REA because it is more time-consuming and less cost-effective, although the results are consistent with those of the REA.”

These comedogenicity tests are probably too sensitive and over dramatise the risks of ingredients blocking pores. It sounds like rabbit ears are particularly prone to blocked pores, and the experiments involving men’s backs aren’t exactly real life situations. You don’t normally apply such high concentrations of singular ingredients. Normally ingredients are in much lower concentrations in cosmetics (The exception to this are pure plant oils. Applying any 100% plant oil to your face on a daily basis might clog pores, eg neat Coconut oil might be a recipe for pore clog central. Some people will be totally fine doing that but it’s a risk, particularly if you’re genetically prone to clogs.). 

What Ingredients Were Flagged as Risky 

One of the studies done in 1989 studied more than 200 ingredients so they were able to further understand the characteristics of the substances that caused issues. Some of this is a bit dry but the thing that I’m most interested in is plant oils. 

Very committed listeners might remember the episode about Dr Sam Bunting when she said that she sees a lot of blocked pores in people who are applying pure plant oils to their face and she always tells people to stop doing that and I haven’t used one since. 

Products/Ingredients to be wary of-

• Makeup– Red pigments are flagged as pore blocking in some studies, depending on what they are dissolved in. So if you’re getting issues in the upper cheek are, suspect your blusher or bronzer
• Butters– Plant butters like Cocoa Butter 
• Oils– Pure plant oils as I just said- Most comedogenic oils included cocoa butter and coconut oil.

Moderately comedogenic oils included sesame oil, corn oil, avocado oil, evening primrose oil, mink oil, soybean oil, and cotton seed oil.

Least comedogenic oils included olive oil, sandalwood seed oil, almond oil, apricot kernel oil, and mineral oil.

Non-comedogenic oils included safflower oil, sunflower oil, and mineral oil.

• Soaps– Bar soaps specifically. “Conventional soaps include salts of fatty acids; the latter are known comedogens. The obsessive use of soaps by patients with acne vulgaris may aggravate the disease and result in its extension to unusual locations.” (Mills & Kligman, 1975)
• Some ingredients which have a great skincare record show up in these comedogenicity tables rather confusingly. Vitamin E (tocopherol), Vitamin A (retinol), Salicylic Acid. Make of that what you will.

I have a list from acne.org of ingredients that showed up in multiple Rabbit ear studies as being problematic- (we will list these on our site)

Linseed Oil, Cocoa Butter, Butyl Stearate, Oleic Acid, Acetylated Lanolin Alcohol, Lanolin Acid, Coconut Oil, Isopropyl Myristate, Isopropyl Isostearate, Isopropyl Linoleate, Myristyl Lactate, Myristyle Myristate, Isopropyl Palmitate, Laureth 4, Oleyl Alcohol, Octyl Palmitate

After boiling my brain reading through some of this research, it looks like there is a lot of variability between studies. For example, one study found Olive oil had a score of 0 in one study and 2.5 in another study. 

Does Vaseline Block the Pores?

You might see this put about on blog posts and social media that vaseline can clog the pores. This rumour started most likely because a 1972 study by Kligman had Vaseline TM as the most likely petrolatum product to cause blocked pores, There has been more recent, more thorough research by Kligman himself in 1996 that this is not the case. He went back and used a different more real life test to find out if his original findings held any water. Nope. They used 10 acne prone teenagers and applied Vaseline to their entire face for 8 weeks and their acne improved.

Kligman says- “Chemical structure determines comedogenicity. As yet, acnegenicity cannot be predicted by structure. The mechanism underlying comedogenicity is unknown. Why corneocytes stick to each other to form horny impactions is still a mystery”

So Should We Pay Attention to the Comedogenic Rating?

Not so much,

The studies are outdated and over stress the comedogenicity of ingredients. Plus these ingredients are not in pure form, substances have a completely different effect when they are within a product. Zoe Draelos who is a big cheese in the world of skincare research did a study “A re-evaluation of the comedogenicity concept” in 2006 and her parting statement on the matter was “Finished products using comedogenic ingredients are not necessarily comedogenic.”. She performed comedogenicity testing on humans using skincare products that contain comedogenic ingredients 

I’m showing Natalie what appears to be a boring table bur actually its not boring, it shows that comedogenic ingredients have a lower comedogenicity when they are in low concentrations.

What Should We Do If We Have Blocked Pores?

The comedogenicity of a product is a very personal thing. One man’s trash is another man’s treasure. It’s only through careful experimentation that you can find out if a product clogs your specific pores, you can’t rely on the comedogenic ratings- they have proven to be too variable and non specific to real life situations. Nevertheless, here are some pointers for frustrated acne sufferers-

• Consider avoiding the high risk ingredients in the above list if you are highly clog prone and something appears to be giving you blocked pores
• Check the top of the ingredient list, the higher the percentage of the chemical, the more likely it is to cause a problem
• Patch testing on an acne prone area can help to
• It’s always a good idea to start products one at a time particularly if you have acne or pore issues 
• Go back to our last episode on blackheads for some good product recommendations

References

Draelos ZD, DiNardo JC. A re-evaluation of the comedogenicity concept. J Am Acad Dermatol. 2006 Mar;54(3):507-12. doi: 10.1016/j.jaad.2005.11.1058. PMID: 16488305.

Fulton, J. E. Comedogenicity and irritancy of commonly used ingredients in skin care products. J Soc Cosmet Chem 43, 321 – 333 (1989). http://www.nononsensecosmethic.org/wp-content/uploads/2013/12/Comedogenicity-and-irritacy-of-commonly-used-ingredients.pdf

Katoulis, A. C., Kakepis, E. M., Kintziou, H., Kakepis, M. E., & Stavrianeas, N. G. (1996). Comedogenicity of cosmetics: a review. Journal of the European Academy of Dermatology and Venereology, 2(7), 115-119.

Kligman, A. M. Petrolatum is not comedogenic in rabbits or humans: A critical reappraisal of the rabbit ear assay and the concept of “acne cosmetic.” J Soc Cosmet Chem 47, 41 – 48 (1996).https://www.insolitbeauty.com/documentacion/A%20critical%20reappraisal%20of%20%20the%20concept%20of%20acne%20cosmetica.pdf

Kligman, A. M. & Mills, O. H. Acne cosmetica. Arch Dermatol 106, 843 – 850 (1972). https://www.ncbi.nlm.nih.gov/pubmed/4264346