Simply speaking: comedogenic
What is the meaning of comedogenic?
"Comedo" is Latin for blackhead - dirt or fatty matter in a skin duct. "Genic" means "producing" or "favoring"- as in photogenic.
Comedogenic therefore literally means "blackhead causing", and is conventionally accepted to be acne-causing, since clogged pores are an important cause of acne.
What are comedogenic and non-comedogenic ingredients?
The average adult has around 5 million pores on his skin (one for each hair, which is all over the body, even if invisible). Ingredients that have the tendency to accumulate in the pores and jam them up are comedogenic. Ingredients that do not have this tendency are non-comedogenic. These are the two extremes, and there are lots of ingredients in between.
What happens when pores are blocked?
The skin is a very active organ within, although it looks calm on the outside. When pores clog, the natural excretion of sebum and dead cells from the skin reduces. This leads to, you guessed it - comedos! This build-up is a great place for bacteria to establish themselves, and when they do that, the skin responds with redness and swelling, which is what we see as acne or pimples.
So I should avoid comedogenic ingredients?
If you have very oily, acne-prone skin - yes. Otherwise I wouldn't worry too much about comedogenicity, provided I am regular with cleansing, moisturising and exfoliating my skin.
How do I know which ingredients are comedogenic?
There are lots of half-truths floating around, but two good lists can be found here and here. You can also ask us by sending us a mail at firstname.lastname@example.org
I have acne-prone skin. What should I do?
This question needs a detailed answer and we promise to answer this for you soon. There are tons of resources out there but don't believe everything you read or see on advertisements! Understand the science behind things, and you will be able to choose smartly.
Cheers, Be Good!