A sebaceous cyst is a closed sac under the skin filled with a cheese-like or oily material.
Alternative NamesEpidermal cyst; Keratin cyst; Epidermoid cyst; Epidermal inclusion cyst
Causes, incidence, and risk factors
Sebaceous cysts most often arise from swollen hair follicles. Skin trauma can also cause a cyst to form. A sac of cells is created into which a protein called keratin is secreted.
The main symptom is usually a small, non-painful lump beneath the skin. The lump is usually found on the face, neck and trunk. It usually grows slowly and is not painful.
If the lump becomes infected or inflamed, other symptoms may include:
- Skin redness
- Tender or sore skin
- Warm skin in the affected area
- Grayish-white, cheesy, foul-smelling material that drains from the cyst
Signs and tests
In most cases, your doctor can make a diagnosis by examining your skin. Sometimes, 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 drain it or perform surgery to remove it.
Cysts may become infected and form painful abscesses.
Cysts may return, even after they are surgically removed.
Calling your health care provider
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: A Color Guide to Diagnosis and Therapy. Philadelphia, Pa.: Elsevier Mosby; 2009:chap 20.