What Exactly Is Sebum, and Why Is It So Important?

What's oily, a bit waxy, and secreted from your skin head-to-toe? Though it may not be the most pleasant-sounding skin-care term, sebum is a crucial component of the skin barrier — and when it's thrown off balance (which can happen for a number of reasons), a variety of issues can occur. What's more, though the terms sebum and oil are sometimes used interchangeably in reference to skin, they are not one and the same.

"When people refer to oil on the skin, sebum is generally thought to be one component of it," explains Marisa Garshick, a board-certified dermatologist in New York City. "But [oil] also often includes sweat and other environmental buildup that can occur on the skin."

So then what exactly is sebum and where does it come from? To find out more, including why sebum is so important to overall skin-barrier health, we spoke to a slew of dermatologists. Consider this sebum 101: Here is everything you need to know.

To get technical, sebum is "a complex mixture of fatty acids, sugars, waxes, and other natural chemicals that form a protective barrier against water evaporation," explains Karen Hammerman, a board-certified dermatologist at Schweiger Dermatology Group in Garden City, New York. To get even more technical, the composition of sebum is made up of "triglycerides, wax esters, squalene and free fatty acids, which together help to keep the skin moisturized," Garshick explains.

So again, "what we call 'oil' on our skin is made up of more than just sebum," Hammerman says. "It also contains a mixture of sweat, dead skin cells, and tiny particles of whatever else is in the dust floating around you."

In sum: Sebum and oil are not one and the same. Rather, sebum is just one of the many components of oil.

Sebum is produced by the sebaceous glands, which naturally cover our bodies from tip to toe. There are two types of sebaceous glands: Those that are connected to a hair follicle, and those that are not.

"Sebaceous follicles are most commonly found on the face, behind the ears, and on the upper portions of the chest and back," explains Ramin Fathi, a board-certified dermatologist in Phoenix, Arizona. On the face itself, you'll find the highest concentration of sebaceous glands around the T-zone, which is why this area is generally more prone to developing acne.

All sebaceous glands are also considered exocrine glands, meaning that they secrete their content directly onto the skin's surface, explains Caren Campbell, a board-certified dermatologist in San Francisco (rather than endocrine glands, which release their contents into the bloodstream). Other examples of exocrine glands include sweat glands, mammary glands, and tear ducts.

As annoying as excess oiliness and shine can be, sebum is actually critical to overall skin health — that is, when it's not over- or under-produced by the body. On the most basic level, sebum serves as a protective and moisturizing barrier on the surface of the skin, helping to prevent water loss. In addition to helping maintain essential hydration levels that keep skin protected, sebum "can also provide anti-inflammatory, antioxidant, and antibacterial benefits through its different components," Garshick says.

How does that work? "The lipids secreted by sebaceous glands create a slightly acidic film on the skin — a pH of 4.5 to 6.0 — which defends against bacteria, viruses, and other microbes," Hammerman explains. Sebum also may prevent fungal infections like ringworm.

One specific component of sebum, squalene — which is naturally produced by our body (versus squalane, with an a, which is the saturated and shelf-stable version that you'll find in many of your skin-care products) — has also been shown to have UVA protective properties (aka can potentially protect the skin against sunburn and UV damage).

But, you know what we're about to say next: "Squalene can have antioxidant benefits that can help protect against free radical damage caused by environmental exposures, but it does not replace daily use of sunscreen," Garshick explains. Applying SPF every day — no matter your skin tone, the weather, or whether or not you'll even go outside — is still always a must.

Like anything in life or within the body, balance is critical, and the same holds true in regard to sebum production. And, like other components of the skin (such as hyaluronic acid), the level of sebum that our bodies naturally produce fluctuates throughout life.

"Sebum production tends to be pretty high at birth, which is why we see babies with 'cradle cap,' as this is due to an overproduction of sebum," Fathi explains. "Production soon declines until puberty, when it spikes again, which coincides with when most people experience significant acne."

This spike is due to — you guessed it — hormones; specifically androgens. After our teenage years, sebum production in the skin is thought to remain pretty steady through mid-adulthood, after which it continuously declines (thus contributing to drier skin as we age). Hormones, whether they fluctuate naturally or because of a medication or underlying condition, are the primary driving force behind sebum production.

"Pituitary, adrenal, ovarian, and testicular conditions can cause either an increase or decrease in production," Hammerman explains, while hormonal medications often increase sebum production. Birth control pills, antiandrogens, and isotretinoin typically decrease sebum production, which is why they are often helpful in treating or managing acne.

In the case of sebum, too much of a good thing is not a good thing — in fact, it can cause plugged-up glands (called sebaceous hyperplasia) and breakouts. "If you have acne, you likely suffer from too much oil production," Campbell explains. Another condition, seborrheic dermatitis, can develop when an overproduction of sebum mixes with yeast, creating symptoms like flaking, red and itchy skin on the forehead, cheeks, and scalp.

That said, too little sebum makes for dry skin, and can even show up as eczema, Campbell says, which is an impaired skin barrier that needs to be restored.

If you experience any of the aforementioned skin issues and suspect that either an over or underproduction of sebum may be to blame, your best bet is to visit a board-certified dermatologist rather than trying to diagnose and treat it yourself. Though, for mild cases, Campbell recommends treating excess oil with a topical retinoid or, if you're experiencing breakouts, benzoyl peroxide. On the flip side, Campbell says mild cases of dry skin and eczema may be helped by using moisturizers formulated with skin barrier-strengthening ingredients, such as ceramides.

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