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Sebaceous glands are present across your entire skin surface, excluding the palms and soles. These glands play a crucial role in skin health.
Marili Forastieri/Photodisc/Getty ImagesSebum is a double-edged sword for your skin. In the right quantity, it acts as a protective barrier. However, excess sebum can lead to acne, while insufficient amounts may cause dryness and cracking.
Sebaceous glands, responsible for sebum production, are distributed throughout your skin, except on the palms and soles. The density of these glands varies by body part. Areas like the back, forehead, and chin are densely populated, housing between 2,600 to 5,800 glands per square inch. Even the ear canal contains these glands [source: New Zealand Dermatological Society].
Sebaceous glands, with their rounded shape, are located just beneath the skin's surface in the dermis. Sebum travels from the dermis to the skin's surface via pores or hair follicles [source: KidsHealth]. The connection between sebum and hair follicles is vital. Each hair resides in its own follicle, which starts in the subcutaneous layer below the dermis. The sebaceous gland connects to the follicle in the dermis, secreting sebum through it.
Now that you understand the fundamentals of sebum, continue reading to explore its functions in greater detail.
Function of Sebum
Sebum serves multiple purposes. Once it reaches the skin's surface, it acts as a waterproof barrier. It prevents excessive water absorption and loss, while also shielding the skin from bacterial and fungal infections.
While sebum is essential for skin health, excess sebum can lead to issues. Clogged hair follicles, caused by sebum and dead skin cells, create an environment for bacteria, resulting in acne [source: Mayo Clinic]. Whiteheads form from clogged follicles below the surface, while blackheads occur on the surface. If the follicle wall ruptures due to buildup pressure, sebum leaks into surrounding tissue, forming pustules [source: WebMD].
Sebum production begins at birth and continues throughout life, though it fluctuates due to various factors. Puberty marks the peak of sebum production, with males experiencing a more than twofold increase [source: New Zealand Dermatological Society]. Hormonal shifts, such as those during menstruation, pregnancy, and menopause, can also elevate sebum levels [source: American Academy of Dermatology]. As you age, sebum production typically declines, leading to drier skin in older individuals [source: WebMD].
Curious about the components of this oily substance called sebum? Read on to uncover its composition.
Seborrhoea refers to excessive sebum production. While not usually linked to other health issues, it can result in an overly shiny complexion and makeup smudging [source: New Zealand Dermatological Society].
Sebum Composition
Sebum consists of lipids, or fats, which are water-insoluble. This property allows sebum to form a protective barrier, retaining moisture in the skin while repelling external water. Lipids contain carbon, hydrogen, and oxygen, and are present in both plant and animal cells [source: Medicine Net].
Sebum is composed of various lipids, such as cholesterol, glycerides, fatty acids, squalene, wax esters, and cholesterol esters. Its composition changes with age. Newborns have sebum similar to adults, but after six months, it shifts to contain more cholesterol and less wax and squalene. Further changes occur around age eight and during puberty [source: New Zealand Dermatological Society].
To learn more about sebum, explore the resources listed on the next page.
The bacteria Propionibacterium acnes, commonly found on the skin, multiplies rapidly when sebum gets trapped in hair follicles, playing a key role in acne formation [source: Mayo Clinic].
