In simplest terms, sebum is just oil secreted by your skin’s sebaceous glands. Sebum is actually Latin for “fat,” which makes sense, and every square inch of your skin—with the exception of the palms of your hands and the soles of your feet—has it.
Most of us tend to focus on the negative side of sebum, such as its ability to make your face look shiny, and its connection with acne. But the presence of sebum is actually good for your skin since it protects the skin from losing moisture. Yet another good thing about sebum is that it contains a lot of vitamin E, an antioxidant that protects the skin from aging as well as cancer. (The skin on the lips does not make sebum, which is why this area is more prone to skin cancer.)
Dermatologists are intrigued by the components of sebum, which seems to be determined by your individual genetic makeup. Upon taking a closer look, researchers have found sebum contains triglycerides, diglycerides, fatty acids, wax esters, squalane and cholesterol—why is why cosmetic chemists incorporate some of these ingredients in anti-aging creams. It was once believed that squalane levels in the sebum contributed to acne, but again, no definitive link has been made. Squalane is often added to skin creams so those with oily and acne-prone skins should avoid this ingredient to be on the safe side.
People who are prone to acne tend to produce higher-than-average amounts of sebum. This gives them oily skin – seborrhea, as it is called. Seborrhea has no direct link with what you eat; the fats and oil in your diet are broken down by the digestive system, and there is no pathway from there to the skin.
Nor is sebum production influenced by anything you apply to your skin. No matter how dry or tight they may make your face feel, astringent soaps, lotions, or cosmetics that mop up oil on the skin’s surface cannot retard sebum output. Nor, contrary to popular belief, do they stimulate the sebaceous glands to overcompensate by stepping up oil production to lubricate the dried-out surface. Sebum output is strictly under the domination of hormones that are indifferent to cleansers, toners, and other topical oil-control treatments.
The connection between hormones and sebum does not necessarily mean that if you have excess oil on your face, your body is producing an overabundance of testosterone, or that your skin boasts an excess follicle-stimulating DHT. It is instead, typically, a sign that your sebaceous follicles are super-sensitive to these hormones and that they overreact to them, sending out the gush of shine-creating oil that is the most common feature of acne-prone skin.