cosmetic chemistry terminology: sebum


what is sebum? - cosmetic composition

image from BirchBox


As followers of beauty and health, you have most likely heard the word sebum before. This buzz word is used in the context of our skin, face and hair, but what exactly is sebum?

what is sebum?

Sebum is the oil naturally produced by our body which is excreted from sebaceous glands that lie under the first layer of our skin. Sebaceous glands are found everywhere in our skin, which is why sebum can affect our skin, face, hair and nails. According to an article from How Stuff Works, there are approximately “2,600 to 5,800 sebaceous glands per square inch” of our skin.

what does sebum do?

Essentially sebum is what makes our skin “waterproof”. By creating a barrier, much similar to a cell membrane wall, sebum allows our skin to take in certain amounts of water. It can also help prevent too much water from leaving and entering our skin. Too much sebum can cause issues such as acne, overly oily skin, and clogged hair glands, which can also explain the terrible years known as puberty. Sebum production is at a max during puberty and slowly decreases with age.

(Side note: if you’re looking for a mask to soak up all that extra sebum, I’d highly recommend this one!)

There is still a lot of controversy revolving the issue of oil production, oily skin, and sebum regulation. The authors from the Beauty Brains have gone very in-depth with these issues.

the composition of sebum

The reason sebum is able to make our skin “waterproof” is because sebum consists of oils, which are hydrophobic. According to the same article from How Stuff Works, the composition of sebum is not altered with age. Sebum consists of lipids, fatty acids, squalenes, waxes, esters, etc. All compounds that are oily and hydrophobic. Because of its properties, squalene is often used in the formulation of cosmetic products because of its ability to blend in with our skin, creating a soft texture and act as a hydrating agent.


I hope this little cosmetic chemistry terminology lesson taught you a bit about what sebum is, does, and why it’s used in beauty products!


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