Quick answer. A sebaceous cyst is a benign, keratin-filled lump under the skin that is usually harmless but can become infected. It does not need treatment unless it is bothersome or infected, and it should not be squeezed; a red, painful, swollen cyst should be seen by a doctor.
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A sebaceous cyst is a common, non-cancerous lump that forms just under the skin and is filled with a thick, keratin-rich material. Most commonly seen on the scalp, face, neck, back and trunk, these cysts are usually painless, slow-growing and harmless, though they can occasionally become inflamed or infected. The term sebaceous cyst is widely used, although doctors often more precisely call these epidermoid or pilar cysts.
Many people in Singapore notice a sebaceous cyst as a smooth, movable lump and worry it could be serious. This guide explains what a sebaceous cyst is, how it differs from a lipoma, why it forms, when it needs removal, and the important reasons never to squeeze one yourself.
At a glance
| Feature | Sebaceous cyst | Lipoma |
|---|---|---|
| What it is | Keratin-filled sac in the skin | Soft growth of fat tissue under the skin |
| Feel | Firm, round, just under the skin surface | Soft, rubbery, deeper and doughy |
| Central punctum | Often has a small visible central opening | No central opening |
| Contents if drained | Thick, cheese-like, sometimes smelly material | Fat tissue |
| Risk of infection | Can become red, painful and infected | Rarely infected |
What is a sebaceous cyst?
A sebaceous cyst is a closed sac under the skin that fills with keratin, the protein that makes up the outer skin layer, giving the contents a thick, pale, cheese-like consistency. Despite the common name, most are technically epidermoid or pilar cysts arising from skin or hair follicle cells rather than from sebaceous (oil) glands.
These cysts are benign, meaning not cancerous, and very common. They appear as a smooth, round, movable lump, often with a tiny dark central opening called a punctum. They grow slowly and can stay small and unchanged for years. Common sites include the scalp, face, ears, neck, back and chest. Many people in Singapore live with a small cyst for a long time without any problem.
Symptoms & signs
An uncomplicated sebaceous cyst is usually painless and noticed only as a lump. Typical features include:
- A smooth, round, firm lump just beneath the skin that moves slightly when pressed
- A small central dark spot or opening (punctum) over some cysts
- Slow growth over months or years
- Thick, pale, sometimes foul-smelling material if the cyst is squeezed or ruptures
- If infected or inflamed: redness, warmth, swelling, tenderness and sometimes discharge of pus
A cyst that becomes red, hot, painful and swollen has likely become inflamed or infected and should be seen by a doctor rather than squeezed at home.
Causes & risk factors
Sebaceous cysts form when skin cells that should be shed instead move inward and multiply within a sac, or when a hair follicle or skin opening becomes blocked. Factors that contribute include:
- Blocked or damaged hair follicles
- Minor skin injury or previous inflammation, such as old acne
- A ruptured oil gland or trapped surface skin cells
- Being an adult, as cysts are more common in adulthood than childhood
- In some people, a tendency to develop multiple cysts, occasionally running in families
Most cysts develop for no clearly identifiable reason and are not caused by poor hygiene.
How it's diagnosed
A doctor can usually diagnose a sebaceous cyst by examining the lump, noting its smooth, movable nature and looking for the characteristic central punctum. They will also ask how long it has been present and whether it has changed in size, become painful or discharged.
In most cases no test is needed. If the diagnosis is uncertain, the lump is unusual, deep or growing quickly, or the doctor wants to distinguish it from a lipoma or another growth, an ultrasound scan may be used. When a cyst is removed, the tissue can be sent to the laboratory to confirm it is benign, which provides reassurance.
Treatment options
A small, painless sebaceous cyst that is not bothering you usually needs no treatment at all and can simply be watched. Treatment is considered when a cyst is large, in an awkward or visible place, keeps getting infected, or is uncomfortable. Options include:
- Watchful waiting: leaving a stable, harmless cyst alone
- Treating infection: antibiotics and sometimes drainage if the cyst becomes red, painful and infected; the sac itself often needs removing later to prevent recurrence
- Surgical excision: a minor procedure under local anaesthetic to remove the entire cyst including its sac, which gives the best chance of avoiding regrowth
Minor cyst excision is a common day procedure. As a guide, private removal of a straightforward skin cyst in Singapore typically falls within a market range of roughly S$300 to S$1,000 or more per cyst, depending on size, site, the clinic and whether it is sent for laboratory analysis; complex or multiple cysts cost more. Treatment in restructured hospitals may attract subsidies, and procedures done for a medical (not purely cosmetic) reason may have MediSave use in some settings. Always confirm exact fees and eligibility with the clinic, as this is a typical range only and not a quote. Importantly, never squeeze a cyst yourself, as this can push out contents, cause infection and make later removal harder.
When to see a doctor & which specialist
See a doctor if a cyst becomes red, warm, painful or swollen, starts discharging pus, grows quickly, or if you simply want a lump checked and a definite diagnosis. Seek prompt medical care for an infected cyst with spreading redness, significant pain or a fever, as this may need drainage and antibiotics. Any lump that is hard, fixed, rapidly enlarging, bleeding or otherwise changing should be assessed without delay to exclude other causes. In a rare emergency with severe spreading infection and feeling very unwell, you can call 995 or go to A&E.
For diagnosis, removal or recurrent cysts, a skin specialist can examine the lump and arrange treatment. You can find one through our directory of dermatologists in Singapore.
Related guides
- Best Dermatology Clinics in Singapore — our editorial shortlist
- dermatology clinics directory
- Folliculitis
- Heat rash
- Overactive bladder
- Keloid scars
- Bursitis
Sources
- NHS – Skin cyst
- Mayo Clinic – Sebaceous cysts (epidermoid cysts)
- HealthHub Singapore – Health conditions
- DermNet – Epidermoid cyst
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