Monday Beauty Vocab: Sebum, Your Best Frenemy

If you do weird stuff to your face--you know, like wear makeup--understanding your skin's natural moisturizer will help you keep it healthy.
Publish date:
October 21, 2013
pores, dry skin, oily skin, acne, vocab, dehydrated skin, keratosis pilaris, sebum, terminology

The skin is a huge, 22-square-foot organ that weighs eight pounds and does a wonderful job of protecting the human body while remaining flexible, water-resistant and porous. It is an astounding barrier that keeps your innards inside while letting out sweat and waste. It’s bouncy and resistant and all-around really cool.

Everything that we use cosmetically on the skin mimics something that the skin already does itself. Cleansing? The skin expulses dirt and dead skin cells through the pores. Exfoliation? Your skin sheds 30,000 to 40,000 dead skin cells every hour. Hydration? Your skin has that all figured out: it makes sebum.

What is sebum?

Sebum is what we mean when we talk about “oils” on the face. It is made up of 25% wax monoesters, 41% triglycerides, 16% free fatty acids, and 12% squalene. This is the good stuff: a mix of oils and waxes that act as the natural moisturizers in your skin.

You’ve got tons and tons of sebaceous glands that create sebum all over your body, except for the palms of your hands and the soles of your feet. They are usually attached to a hair follicle: they squirt sebum onto the hair to lubricate its passage to the surface as well as cleaning out any dead skin cells around the hair.

But the place where you have the most sebaceous glands is your back, forehead, and chin, where you’ve got anywhere from 2,600 to 5,800 glands per square inch. The bigger the pore, the more sebum it produces.

What does sebum do?

So what exactly does the sebum do? It makes your skin water-resistant from the inside and the outside, so that not too much water comes in and not too much water goes out. It keeps your skin flexible, so that you can smile, laugh, and cry without getting stuck that way. It also acts as a nutrient delivery service, bringing vitamin E, antioxidants, antimicrobial lipids, and pheromones into the upper layers of the skin.

Sebum is also an important part of the outermost layer of your skin, the stratum corneum. This means the “horny layer” in Latin. It’s a bunch of dead skin cells held together by sebum that protect your live skin cells so that they can grow unmolested by infections, dehydration, and mechanical stress. It looks like a brick wall, with dead skin cells acting as bricks and sebum acting as mortar.

So sebum is quite important to the normal functioning of skin. However, if your skin has too much or too little sebum, things can get thrown out of whack pretty quickly.

What happens if my skin lacks sebum?

Let’s start with the problem of having too little sebum. Skin that under-produces sebum is a skin type referred to as dry skin. This can be caused by a number of things. Older skin produces less sebum than younger skin. A woman’s skin in general produces less sebum than a man’s skin. People with smaller pores produce less sebum than people with larger pores.

Or, you could actually have skin that over-produces sebum, but you remove too much sebum with cosmetic cleansers and acne treatments. This is a skin condition known as dehydrated skin.

If your skin lacks sebum, your stratum corneum will look more like this:

The bricks of dead skin cells are lacking their mortar. They start falling off, which will look like flakes on the skin. The skin will start to look cracked and wrinkled. The stratum corneum is lacking its emollient to hold itself together.

Skincare for skin that lacks sebum

Having too little sebum can be treated cosmetically with emollient-rich moisturizers. Certain lipids will fill in those cracks left by the lack of sebum and smooth out the stratum corneum. This is why rich creams are so effective in reducing the signs of aging: they simply take the place of skin’s natural moisturizer to give the appearance of skin in its youth.

However, if you have skin that over-produces sebum that has been stripped of its sebum by over-washing and acne treatments, those emollient-rich moisturizers won’t do you any favors. Your problem isn’t really lack of sebum, it’s too much sebum.

What happens if my skin has too much sebum?

Sebum over-production can lead to some really common skin problems. The production of sebum is triggered by hormones called androgens that are produced during puberty, before menstruation, during menopause, and because of certain medications and disorders.

When the skin produces too much sebum, it can get mixed up in the dead skin cells that it is trying to expulse and sit around in the pore. This mix of sebum and dead skin becomes a tasty snack for the bacteria on the skin’s surface. The pore becomes inflamed, creating acne. If the sebum mixes with keratin, it can plug up into little bumps called keratosis pilaris.

You probably have had one or both of these conditions. Acne affects 70-90% of teenagers and 25% of adults aged 25-44. Keratosis pilaris affects 50-80% of children and 40% of adults.

Most treatments for keratosis pilaris involve trying to break down and lift out the keratin plug that is blocking the pore. Treatment for acne can also focus on using chemical exfoliators or topical treatments like salicylic acid or benzoyl peroxide to remove the plug of dead skin and sebum. Or it can involve antibiotics for treating the infection.

There are also things you can do to simply stop the over-production of sebum in the first place. Taking birth control pills that contain both estrogen and progesterone will lower the amount of androgens in your body and thus slow the production of sebum. You can also take an oral retinoid treatment, isotretinoin (Accutane), which will also slow sebum production.

Skincare for skin that over-produces sebum

However, simple cosmetic skincare can sometimes be the best option. One of the best ways to remove extra sebum from your face is with a cosmetic cleanser. You don’t need a particularly harsh one; in fact, that’s one of the best ways to go into cracked-brick-wall sebum-lacking territory. A simple, gentle, soap-free cleanser will break down the extra sebum without damaging your stratum corneum. An oil cleanser, if formulated to be noncomedogenic, or occlusive-agent-free, will do a good job of dissolving sebum without inciting another breakout.

If you have stripped off too much sebum by using harsh cleansers or acne treatments, your skin does in fact lack lipids in your stratum corneum. However, if you use rich, buttery moisturizers to treat your skin, you risk choosing a product with a heavy occlusive agent like petrolatum, shea butter, coconut oil, mineral oil, paraffin, beeswax, or lanolin.

Occlusive agents work by creating a seal on top of the skin to do the job of the damaged stratum corneum, to keep water inside the skin. This is great for skin that is not prone to acne. However, skin that over-produces sebum is likely to react to having its sebum stripped off by producing even more sebum to compensate. If you have an occlusive agent on top of your skin, the overabundant sebum will get trapped in the pores and lead to another breakout.

It is thus more beneficial to treat your skin with a humectant and a non-occlusive emollient moisturizer to draw water to your skin while it reproduces the sebum necessary to repair your stratum corneum.

Sebum: your best frenemy

Sebum, in general, is great stuff. If your skin is acting normal and producing sebum in the right quantity, there is nothing better for keeping your skin healthy. As long as you aren’t doing weird stuff to your face, like using makeup, sebum is perfectly effective in cleaning up your skin and keeping it moisturized and beautiful.

Like many people, I put a lot of weird stuff on my face in the form of makeup, sunscreen, and anti-aging treatments. I also have skin that over-produces sebum. Thus, I have to be careful to keep the sebum levels in my skin at a healthy level with by preventing over-production with hormonal birth control, removing extra sebum with cleanser, and repairing any damage I do to my stratum corneum with an occlusive-free moisturizer.

Your skin’s sebum level is unique to you and will likely change a many times in your life. Understanding how to help your skin stay balanced will help you deal with the crazy changes in your skin over the years.