ConditionSkin, hair & nails
Epidermal Cysts
An epidermal cyst is a common, harmless, slow-growing lump under the skin, filled with a soft, cheesy, often smelly material called keratin. It usually appears on the face, neck, chest, upper back or scalp and often has a tiny dark pore on top. Many people call them sebaceous cysts, though they do not come from oil glands. Most need no treatment, but a cyst that becomes red, swollen and painful may be inflamed or infected and needs care.
Also called: Epidermoid cyst, epidermal inclusion cyst, infundibular cyst, keratin cyst, sebaceous cyst (common but inaccurate name)
At a glance
- What it is
- A sac under the skin lined with skin cells, filled with keratin.
- Where
- Face, neck, chest, back, scalp, behind the ears, genitals.
- Looks like
- A smooth, round, movable lump, often with a central pore (punctum).
- Complications
- Inflammation or infection, rupture. Cancer is extremely rare.
- Treatment
- None if harmless. Warm compresses or drainage if inflamed. Surgical removal of the whole sac to prevent recurrence.
When to get help
See a doctor within a day or two
- A cyst that becomes red, hot, swollen and very painful, especially with fever or spreading redness
- Red streaks spreading from a cyst, or feeling generally unwell
Book a routine appointment
- A cyst that keeps getting inflamed or bothering you
- A lump that is growing quickly, is hard and fixed, bleeds or ulcerates
- Many cysts, especially in a young person, or cysts with bowel symptoms or family history of colon polyps
- Wanting a cyst removed for comfort or appearance
Usually safe to manage at home
- A small, smooth, painless, movable lump that has not changed
- A mildly tender cyst: warm compresses several times a day
What an epidermal cyst is
Epidermal cysts form when cells from the outer layer of skin (the epidermis) end up beneath the surface, often in a blocked or damaged hair follicle, and keep growing. They form a closed sac and shed keratin, a protein, into it. Because the sac has no way to drain, the keratin collects, forming a lump.
They are sometimes called sebaceous cysts, but true sebaceous cysts (steatocystomas) come from oil glands and are less common. The terms "epidermal cyst" and "epidermoid cyst" mean the same thing.
What they look like
- a dome-shaped lump, usually 0.5 to 5 cm across
- skin-colored, white or yellowish
- smooth and firm or slightly rubbery
- moves slightly when pushed
- often a small dark central pore (punctum)
- may release a thick, white, cheesy, foul-smelling material if squeezed
Causes and risk factors
- blocked hair follicles, often linked with acne
- skin injury, surgery or piercing, which can push surface cells deeper (epidermal inclusion cyst)
- sun damage
- more common in adults aged 20 to 50 and in men
- Gardner syndrome: an inherited condition with many cysts, bowel polyps and bone growths. Multiple cysts in childhood should be checked.
- Gorlin syndrome and some other rare genetic conditions
Inflamed and infected cysts
A cyst can suddenly become red, swollen and painful. This is often caused by the cyst wall rupturing under the skin: keratin leaks into the surrounding tissue and triggers intense inflammation, which may or may not involve infection. Squeezing a cyst makes this more likely.
Signs:
- rapid swelling and tenderness
- redness and warmth
- pus may drain
- fever or spreading redness suggests infection
Epidermal cyst vs other lumps
| Lump | Feel | Clues |
|---|---|---|
| Epidermal cyst | Firm, round, movable | Central pore, cheesy contents |
| Pilar cyst | Firm, smooth | On the scalp, no pore, often runs in families |
| Lipoma | Soft, doughy, rubbery | Fatty, deeper, no pore |
| Abscess or boil | Tender, warm | Rapid onset, pus |
| Milia | Tiny, hard, white | 1 to 2 mm, around eyes and cheeks |
Diagnosis
Most epidermal cysts are diagnosed by appearance and feel. Ultrasound can help with deep or unusual lumps. If a lump is hard, fixed, fast-growing or unusual, the doctor may remove it and send it to a lab.
Treatment
Leave it alone
Small, painless cysts do not need treatment. Do not squeeze or pick them, which can cause rupture, inflammation, infection and scarring.
Inflamed cysts
- Warm compresses several times a day may help it settle or drain.
- Steroid injection into the cyst reduces inflammation quickly.
- Incision and drainage: a doctor opens the cyst to release pus and keratin. This relieves pain but leaves the sac behind, so the cyst often returns.
- Antibiotics only if there are signs of infection spreading into the skin.
Removal of the whole cyst is usually delayed until inflammation has settled, which makes surgery easier and cleaner.
Removal
- Surgical excision: the whole sac is removed under local anesthetic, and the skin is stitched. Removing the entire wall greatly reduces the chance of recurrence.
- Minimal excision or punch technique: a small hole is made, contents squeezed out, and the sac pulled through, leaving a smaller scar.
- Laser techniques are used in some clinics.
Removal for cosmetic reasons may not be covered by insurance.
Outlook
Epidermal cysts are benign. Cancer arising in an epidermal cyst is extremely rare. Cysts that are not removed completely can recur. New cysts can develop elsewhere.
Frequently asked questions
What is the difference between an epidermal cyst and a sebaceous cyst?
Most lumps called sebaceous cysts are actually epidermal cysts, which come from the outer skin layer and contain keratin. True sebaceous cysts arise from oil glands and are less common. The treatment is the same: leave alone if harmless, or remove surgically if bothersome.
Should I pop an epidermal cyst?
No. Squeezing can rupture the cyst wall under the skin, causing painful inflammation, infection and a larger scar, and the cyst will usually come back. If it bothers you, a doctor can drain or remove it properly.
Why does my cyst smell?
The keratin inside the cyst breaks down and is acted on by skin bacteria, producing a cheesy, unpleasant odor. Smell alone does not mean infection. Redness, swelling, heat and increasing pain do.
Will an epidermal cyst go away on its own?
Sometimes a cyst shrinks after draining, but it usually refills because the sac remains. Only surgical removal of the entire sac reliably prevents the cyst from returning.
Sources
This guide was written from current patient and clinical guidance, including:
- American Academy of Dermatology: Cysts, overview and treatment
- American Osteopathic College of Dermatology: Epidermoid cyst
- DermNet: Epidermoid cyst
- MedlinePlus: Epidermoid cyst
- British Association of Dermatologists: Epidermoid and pilar cysts patient leaflet