An epidermal cyst is a growth that develops on the skin. It is also known as an epidermoid, sebaceous, or keratin cyst. These typically benign masses are most commonly found on the areas from the neck to the top of the head and the trunk, though they can grow on any part of the skin. They are among the most common kinds of cysts. Most epidermal cysts can be ignored and may even go away on their own, but in some cases removal may be required.
Many epidermal cysts begin to grow due to swollen hair follicles. The blockage caused by the shrinkage of space in the follicle results in a back-up of fluid and the accumulation of cells known as keratin. When this material cannot properly exit the body, it builds up until it eventually develops into a cyst. The growth may also happen as a result of trauma to the skin, such as with surgery.
On rare occasions, this type of cyst can become sore and inflamed, or develop abscesses. If the mass becomes uncomfortable or infected, it can be injected with steroids so that it will shrink. Larger cysts may need to be removed surgically. The application of moist warmth over the cyst, such as with a damp cloth, may also help it to drain on its own. Once a cyst has been cleared, the area will usually heal permanently, though it is possible for the growth to return.
The material in an epidermal cyst is usually a combination of a thin, oily fluid and a thicker mass similar in texture to a soft cheese. In most cases, the fluid is harmless. If bacteria enter the cyst, there may also be pus due to infection.
Although most cysts can be safely ignored, they can be similar in appearance and texture to other more serious growths on the skin. If a growth does not go away after the application of moist warmth, it is usually advisable to have it examined by a doctor so that diseases such as cancer can be ruled out. Most cysts will develop over a long period of time and maybe even several years.
Milia is a common type of epidermal cyst. These growths are smaller than the typical variety and usually grow in groups. Infants will often develop milia, though they can be found at any age. Milia may also develop as the result of procedures such as dermabrasion or following blistering of the skin.