Despite popular belief, it's not quite the same thing as oil. Dermatologists break down the exact makeup of sebum, how it changes as we get older, and what to do if your skin produces too much or too little. 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. 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? 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. 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. So again, "what we call 'oil' on our skin is made up of more than just sebum. 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.
Where Does Sebum Come From?
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. 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 (rather than endocrine glands, which release their contents into the bloodstream). Other examples of exocrine glands include sweat glands, mammary glands, and tear ducts.
Why Is Sebum Important?
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.
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. 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. 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. 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. 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, while hormonal medications often increase sebum production. Birth control pills, anti-androgens, and isotretinoin typically decrease sebum production, which is why they are often helpful in treating or managing acne.
Too Much vs. Too Little Sebum:
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. 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, 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, is recommended treating excess oil with a topical retinoid or, if you're experiencing breakouts, benzoyl peroxide. On the flip side, mild cases of dry skin and eczema may be helped by using moisturizers formulated with skin barrier-strengthening ingredients, such as ceramides.
