Medical Dermatology

Epidermal Cyst

A firm lump under the skin, sometimes with a small central opening, that may sit quietly for years and then suddenly become red and painful. Epidermal cysts are benign — but they do not resolve on their own, and how they are managed depends on whether they are inflamed.

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At a glance

What it is: A benign cyst arising from the upper part of a hair follicle, lined by epidermis-like tissue and filled with keratin.
Also called: Epidermoid cyst, epidermal inclusion cyst, infundibular cyst, keratin cyst. Often called a “sebaceous cyst” — a misnomer, as it contains no sebum.
Who it affects: Most often adults in young to middle age, and around twice as commonly in men.
Common sites: Central trunk — chest and shoulders — and the face, though they can occur almost anywhere.
Treatment: Observation if quiet; drainage if acutely inflamed; complete excision of the cyst wall for definitive removal.

Understanding the condition

What is an epidermal cyst?

The skin's surface layer continually produces keratin, the tough protein that normally sheds away invisibly. An epidermal cyst forms when a pocket of that surface-type tissue ends up beneath the skin, enclosed in a thin sac. It carries on producing keratin, which has nowhere to go — so the cyst slowly enlarges.

Most arise from an occluded pilosebaceous unit — a blocked hair follicle. On areas without hair, such as the palm, sole or buttock, they can instead follow an injury that drives skin cells into the deeper layer.

What it looks and feels like

A firm, flesh-coloured or yellowish nodule, typically 1–3cm across
Attached to the skin surface but mobile over the deeper tissue
Often a central punctum — a small dark opening, which becomes more obvious when the lesion is gently squeezed from the sides
Cheesy, unpleasant-smelling material may be expressed from that opening
Usually causes no symptoms at all unless it ruptures

A note on the name“Sebaceous cyst” is in common use but is not accurate — these cysts do not involve the sebaceous glands and contain no sebum. If a previous doctor used that term, they were almost certainly describing this same benign lesion.

When it flares

The inflamed cyst

A quiet cyst can become suddenly swollen, red, hot and tender over a day or two. This is usually because the cyst wall has ruptured and keratin has escaped into the surrounding dermis, where it provokes an intense inflammatory reaction.

An important practical point follows: this is generally inflammation rather than infection. It can look and feel very like an abscess, but the underlying process is a reaction to the cyst's own contents. Consequently, antibiotics are frequently not required, and routine swabbing for culture is not usually recommended.

What an acutely inflamed cyst does need is assessment. Incision and drainage relieves the pressure and settles symptoms. Definitive excision is usually deferred until the inflammation has resolved, because an actively inflamed cyst is considerably more difficult to remove cleanly — and incomplete removal is what causes recurrence.

Please don't squeeze itSqueezing empties some contents but leaves the wall behind, so it refills. More often it forces keratin into the deeper skin and triggers precisely the painful, inflamed swelling you were hoping to avoid — while making later removal harder and the scar less tidy.

Management

How epidermal cysts are treated

The right approach depends on whether the cyst is quiet or inflamed, its size and site, and whether it has been treated or manipulated before.

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Observation

Entirely reasonable for a quiet cyst.

No treatment needed if it is small, painless and not enlarging
Many people live with a cyst for years without difficulty
Worth reviewing if it changes, enlarges or becomes uncomfortable

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For an inflamed cyst

Settling the acute problem first.

Incision and drainage relieves pressure and pain
An intralesional corticosteroid injection may reduce inflammation
Antibiotics are often unnecessary as this is not primarily an infection
Definitive removal is usually planned once inflammation settles

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Definitive removal

Performed under local anaesthetic as a day procedure.

Complete excision of the cyst together with its wall
A minimal-incision technique can suit selected cysts
The wall must be removed entirely to prevent recurrence
Tissue is generally sent for microscopic examination

Your procedure

What removal involves

Cyst removal is carried out under local anaesthetic as a day procedure. You remain awake, the area is numbed, and you go home afterwards.

Two broad approaches exist. Conventional excision removes the cyst and its wall through an incision, which is then closed with sutures. A minimal-incision technique uses a much smaller opening — the contents are expressed and the wall extracted through it — which is attractive in cosmetically sensitive areas, though it is not suitable for every cyst, particularly ones that have been inflamed or manipulated previously.

Which is appropriate depends on the size, site, previous history and the presence of scarring. That discussion happens at consultation, before anything is scheduled. Our surgical dermatology page covers what to expect from skin surgery more generally, including wound care and healing.

Before your procedureTell us about any blood-thinning medication, including aspirin and newer anticoagulants, and about any tendency to thickened or keloid scarring. Do not stop prescribed medication without advice.

Seeking help

When to see a dermatologist

Arrange an assessment if:

A lump is enlarging, painful, or has become red and swollen
A cyst has flared before, or keeps recurring
It is in a site that catches on clothing, or is uncomfortable to lie on
You are uncertain what the lump is
You would like it removed for appearance
You have several cysts, particularly if others in your family do too

Seek prompt medical attention ifthe area becomes rapidly more painful and spreading red, you feel unwell or feverish, or there is significant discharge. These features suggest secondary infection or spreading cellulitis and should be reviewed rather than waited out.

Dr Chen Qiping

Consultant Dermatologist · MBBS, MRCP (UK), M.Sc, FAMS (Dermatology)

Dr Chen practises surgical dermatology, including removal of cysts and other benign lesions, alongside general, paediatric, laser and cosmetic dermatology. Consultations are available in English and Mandarin.

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Common questions

Epidermal cyst — frequently asked questions

Is a 'sebaceous cyst' the same thing?

The term sebaceous cyst is commonly used but is a misnomer. An epidermal cyst does not arise from sebaceous glands and does not contain sebum — it is lined by epidermis-like tissue and filled with keratin. Other names you may encounter for the same lesion include epidermoid cyst, epidermal inclusion cyst, infundibular cyst and keratin cyst. Pilar cysts, which arise from the hair root and are common on the scalp, are a different entity.

Does an epidermal cyst need to be removed?

Not necessarily. A cyst that is not painful, not enlarging and not bothering you can reasonably be left alone. Removal is generally considered when it is inflamed or has ruptured before, when it is enlarging, when it is in a site that catches on clothing or is uncomfortable, when it recurs, or when the appearance is troubling. Occasionally removal is advised because the diagnosis needs confirming.

Why did my cyst suddenly become red and painful?

That usually means the cyst wall has ruptured, releasing keratin into the surrounding skin. Keratin is intensely irritating to the dermis and provokes a brisk inflammatory reaction — swelling, redness, tenderness and sometimes discharge. This is inflammation rather than infection in most cases, which is why antibiotics are frequently unnecessary. It does need assessment, because an inflamed cyst is managed differently from a quiet one.

Can I squeeze it myself?

Please don't. Squeezing may express some of the contents but leaves the cyst wall behind, so the cyst refills. More importantly it commonly causes rupture into the deeper skin, producing exactly the painful inflamed swelling you were trying to avoid, and increases the chance of scarring and of the cyst recurring in a more difficult form.

Will it come back after removal?

That depends on whether the entire cyst wall is removed. If any lining remains, the cyst can reform — which is why complete removal of the wall is the aim of definitive surgery. Incision and drainage relieves an acutely inflamed cyst but does not remove the wall, so recurrence after drainage alone is common and a definitive procedure is often planned later once inflammation has settled.

Will there be a scar?

Any procedure that cuts the skin leaves a mark. The aim is a scar as fine and inconspicuous as possible. A minimal-incision technique can remove some cysts through a very small opening, which is attractive in cosmetically sensitive areas, though suitability depends on the size and site of the cyst and whether it has been inflamed or manipulated before.

Are these cysts a sign of anything serious?

Epidermal cysts are benign, and malignant change within one is exceedingly rare. Occasionally, multiple cysts occurring together can be associated with an underlying genetic condition, which is one reason a doctor may ask about family history if you have several.

References

DermNet. Epidermoid cyst. Author: Megan Lam; DermNet Editor in Chief: Adjunct A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. dermnetnz.org
Mayo Clinic. Epidermoid cysts — Diagnosis and treatment. mayoclinic.org
Chen S, Srivastava D, Nijhawan RI. Removal of large epidermoid cysts by use of a minimal-incision technique. J Am Acad Dermatol. 2017;77(1):e13–e14.

Page last reviewed: 28 July 2026.

Important — This page is general information and is not medical advice. It cannot take the place of an individual consultation, examination and diagnosis. Treatment options, their suitability and their possible side effects should be discussed with a qualified doctor who has assessed you. Individual results vary. If you have concerns about your skin, please arrange a consultation.

Have a lump you would like assessed?

Arrange a consultation with Dr Chen Qiping at our Collyer Quay clinic — two minutes' walk from Raffles Place MRT.

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