A sebaceous cyst is a closed sac under the skin filled with a cheese-like or oily material.

See also:

• Carbuncle
• Cyst
• Furuncle

Sebaceous cysts most often arise from swollen hair follicles. Skin trauma can also induce a cyst to form. A sac of cells is created into which a protein called keratin is secreted.

These cysts are usually found on the face, neck, and trunk. They are usually slow- growing, painless, freely movable lumps beneath the skin. Occasionally, however, a cyst will become inflamed and tender.

The main symptom is usually a small, non-painful lump beneath the skin. However, if it becomes infected, you may have redness, tenderness, or increased temperature of the skin over the area.

Grayish-white, cheesy, foul-smelling material may drain from the cyst.

In most cases, your doctor can diagnose this type of cyst by simply examining your skin. Occasionally, a biopsy may be needed to rule out other conditions.

Sebaceous cysts are not dangerous and can usually be ignored. Placing a warm moist cloth (compress) over the area may help the cyst drain and heal.

If you have a small inflamed cyst, your doctor may inject it with a steroid medicine that reduces swelling.

If the cyst becomes swollen, tender, or large, your doctor may surgically remove it. This procedure is done in the doctor's office.

Large, painful cysts may interfere with day-to-day life.

These cysts may occasionally become infected and form painful abscesses.

The cysts may return after they are surgically removed.

Call your health care provider if you notice any new growths on your body. Although cysts are not dangerous, your doctor should examine you for signs of skin cancer.

Habif TP. Clinical Dermatology. 4th ed. St. Louis, Mo: Mosby; 2004.

Roberts JR, Hedges JR. Clinical Procedures in Emergency Medicine. 4th ed. Philadelphia, Pa: WB Saunders; 2004.