Sebaceous Glands and Causes of Acne

The Simple Science of Why You Get Pimples

Normal skin model on white background
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Sebaceous glands are part of the pilosebaceous unit which contains the hair follicle, hair shaft, and erector pili muscles responsible for goosebumps. Pilosebaceous units are found everywhere on the body except the lower lip, the palms of the hands, and the tops and soles of the feet. The greatest concentrations (and the places acne is most often seen) are on the face, scalp, upper neck, and chest.

The sebaceous glands produce sebum, an oily substance comprised of triglycerides, wax, squalene, and free fatty acids. Sebum keeps the skin and hair moisturized and acts as a waterproofing barrier to prevent them from becoming dry and brittle. It also performs an important function by inhibiting the growth of microorganisms on the skin.

The Association Between Sebum and Acne

While the sebaceous glands typically produce the ideal amount of sebum to keep the skin and hair moisturized, they sometimes don't work well as expected.

By way of example, sebum production tends to slow down at around the age of 20. With the glands less able to produce enough sebum on a regular basis, the skin can become dry and lose elasticity. This is one of the reasons why skin texture changes as you get older.

Conversely, the hormonal changes that occur during puberty cause the sebaceous glands to enlarge and produce more sebum. This overproduction, combined with the shedding of dead skin cells, can clog follicle pores and produce oily skin, known as seborrhea. Acne can develop when the sebum becomes trapped inside these pores, leading to the very common outbreak of adolescent pimples.

Sebum can also cause hair to appear greasy if it hasn't been washed for several days. The eyelids, meanwhile, have their own type of sebaceous glands (called meibomian glands) which secrete a particular kind of sebum into tears. When tears accumulate, they produce a mucousy discharge that can crust over, leading to the hard discharge we often found in the corners of our eyes after sleep.

How Acne Develops

Your pores are self-cleaning machines. They do a great job of constantly clearing out dirt, oil, and dead skin cells. But when this process doesn't work as it should, all of that dirt can become trapped.

Sebum provides moisture to the skin and hair by moving up the hair shaft and out of the hair follicle opening. However, there are times when sebum can act like glue by sticking to dead skin cells on the surface of the skin. Together, this mass of skin and sebum effectively blocks the hair follicle opening, even as the sebaceous glands keep pumping out sebum.

As bacteria start to thrive in the pore, the immune system responds by forming a pimple filled with pus (a combination of sebum, dead skin cells, and dead white blood cells) around the site of infection. A pimple will gradually become red and inflamed as the immune cells attack and kill the bacteria, leading to the eventual healing of the follicle and surrounding tissue.

View Article Sources
  • James WD, Berger TG, Elston DM, Neuhaus IM, Micheletti RG, Andrews GC. Andrews Diseases of the Skin: Clinical Dermatology. Philadelphia, PA: Elsevier; 2016.