Sebaceous Cyst

3 min read·Last updated: 2026-02-08·Reviewed by Dr. Julia Tzu, MD, FAAD, FACMS

At a Glance

A sebaceous cyst, more accurately called an epidermal inclusion cyst or epidermoid cyst, is a small, fluid-filled pocket that forms under the skin. These cysts develop when keratin (a protein in skin cells) and dead skin cells become trapped beneath the skin's surface, forming a capsule that fills with a thick, cheese-like substance. Despite the common name "sebaceous cyst," these growths typically contain keratin rather than sebum (oil). They are benign, slow-growing, and usually painless unless they become infected or inflamed. While they don't require treatment, removal is an option if they're bothersome.

Epidermal inclusion cysts form when keratin and dead skin cells become trapped beneath the skin[1]
Complete removal of the cyst wall (capsule) prevents recurrence[2]
Cysts that are only drained often recur because the sac can refill[2]
Never attempt to pop or drain a cyst at home, as this can cause infection[1]

Symptoms

Small, round, movable bump under the skin
Slow-growing lump
Skin-colored, whitish, or yellowish appearance
Small central opening (punctum) sometimes visible
Thick, cheese-like or cottage cheese-like material inside
Usually painless unless infected
May have unpleasant odor if punctured or infected
Redness, tenderness, and swelling if infected

When to Seek Professional Care

Cyst becomes painful, red, or swollen (infection signs)
Cyst ruptures or drains
Rapid growth or size change
Cyst interferes with daily activities
Cosmetic concerns about appearance
Uncertainty about what the lump is

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Causes

Keratin and dead skin cells trapped under skin
Blocked or damaged hair follicle
Skin trauma or injury
Acne or other skin conditions
Ruptured sebaceous gland
Developmental defect in skin
Genetic predisposition

How We Can Help

We offer a service to help manage this condition: Cyst Removal.

Prognosis

Benign with excellent prognosis
Complete removal including capsule prevents recurrence
Drainage alone often leads to recurrence
Some cysts remain stable for years without treatment
Infection can occur but is treatable
No risk of transformation to cancer

Frequently Asked Questions

What is a sebaceous cyst?

A sebaceous cyst, technically called an epidermal inclusion cyst, is a small pocket under the skin filled with keratin and dead skin cells. They appear as round, skin-colored bumps that grow slowly and are usually painless. Despite the name, they contain keratin rather than oil (sebum).

Are sebaceous cysts dangerous?

Sebaceous cysts are benign and not dangerous. They don't transform into cancer. However, they can rupture or become infected, which causes pain, redness, and swelling. Infected cysts need medical attention. Any new lump should be evaluated by a healthcare provider to confirm the diagnosis.

When should I see a doctor about a cyst?

See a doctor if a cyst becomes painful, red, or swollen (signs of infection), if it ruptures or drains, if it grows rapidly, or if you're uncertain what the lump is. Also consult a provider if the cyst bothers you cosmetically or interferes with daily activities.

How is a cyst removed?

The most effective removal involves surgically excising the entire cyst, including its wall (capsule). This prevents recurrence. Simple drainage provides temporary relief but the cyst often returns because the sac remains. The procedure is usually performed under local anesthesia as an outpatient.

Can I pop a cyst at home?

Never try to pop, squeeze, or drain a cyst at home. This can cause infection, scarring, and the cyst will likely return. Only a medical professional should remove or drain a cyst using sterile technique. Home attempts often make the situation worse.

Do cysts come back after removal?

If only drained, cysts commonly return because the sac can refill with keratin. Complete surgical removal including the entire capsule usually prevents recurrence. Your provider will remove the whole cyst wall to give you the best chance of permanent resolution.

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