An epidermal (skin) cyst is a small, round lump in the top layer of skin called the epidermis. It may be filled with a soft, yellow substance called keratin. Skin cysts most often appear on the face, ears, back, or chest. But they can appear on almost any part of the body.

When you have an skin cyst, the lump or bump under the skin is:

• Small, round, and smooth.
• About the size of a pea, or a little smaller or larger.
• Yellow, white, or skin-colored. It can turn red if it becomes inflamed.
• Painless. But it can be painful if it's inflamed.

An infected cyst will need to be treated by a doctor. This may involve opening it to let the contents out. It may also include taking antibiotics.

If a cyst is inflamed but not infected, or you are bothered by how the cyst looks, your doctor may treat or remove it.