Cysts

Epidermoid inclusion cysts are typically harmless, slow-growing bumps under the skin. They often appear on areas with more hair such as the scalp, face, trunk, upper back, or groin area. Some may have an enlarged pore in the center of them. They are the most common type of skin cyst.

Epidermal cysts are sometimes called sebaceous cysts. But a sebaceous cyst is different from an epidermal inclusion cyst. They are less common. True sebaceous cysts start in the sebaceous gland. This is an oil gland in the skin that produces (secretes) an oily substance called sebum. Sebum lubricates the skin to help keep it healthy. Epidermoid cysts can remain stable. Or they may steadily grow. Sometimes they will become inflamed, red, painful, or suddenly break open (rupture).

Cysts are common and may occur anywhere on the body. A cyst is an invagination of skin, which forms a sack beneath the skin’s surface. Because the lining of this sack consists of normal skin, it continues to shed skin cells just like our skin does. These dead skin cells become compressed and as more accumulate, the cyst grows into a lump. Occasionally, if the sack ruptures beneath the skin, an inflammatory reaction results that causes pain, redness, and drainage of a smelly fluid containing the dead skin cells. If this happens, you should see your dermatologist for treatment to decrease the risk of secondary infection and scarring.