A sebaceous cyst is a closed sac under the skin filled with a cheese-like or oily material.
Epidermal cyst; Keratin cyst; Epidermoid cyst; Epidermal inclusion cyst
Sebaceous cysts most often arise from swollen hair follicles. Skin injury can also cause a cyst to form. A sac of cells is created into which a protein called keratin is secreted. People with these cysts may have family members who also have them.
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
Exams and Tests
In most cases, the health care provider can make a diagnosis by examining your skin. Sometimes, a biopsy may be needed to rule out other conditions. If infection is suspected, you may need to have a skin culture.
Sebaceous cysts are not dangerous. Your provider may suggest home care by placing a warm moist cloth (compress) over the area to help the cyst drain and heal.
A cyst may need further treatment if it becomes:
- Inflamed and swollen – the provider may inject the cyst with steroid medicine
- Swollen, tender, or large – the provider may drain the cyst or do surgery to remove it
- Infected – you may be prescribed antibiotics to take by mouth
Cysts may become infected and form painful abscesses.
Cysts may return if they are not completely removed by surgery.
When to Contact a Medical Professional
Call your provider if you notice any new growths on your body. Although cysts are not dangerous, your provider should examine you for signs of skin cancer. Some skin cancers look like cystic nodules, so have any new lump examined by your provider.
Patterson JW. Cysts, sinuses, and pits. In: Patterson JW. Weedon's Skin Pathology. 4th ed. Philadelphia, PA: Elsevier; 2015:chap 16.
Stone MS. Cysts. In: Bolognia JL, Jorizzo JL, Schaffer JV, eds. Dermatology. 3rd ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 110.