A sebaceous (more correctly epidermoid) cyst is a benign sac under the skin, with a wall that fills with keratin. It is harmless, but it can grow or become inflamed. The crucial point: it comes back unless the whole wall is removed — simply "emptying" it is not enough. The definitive solution is complete removal, ideally when it is not inflamed.
A skin cyst is one of the most common "lumps" that bring people to the clinic — and one of the most misunderstood. Many try to "squeeze" it, or watch it return after a quick lancing. Let's look at why that happens and what the correct treatment is.
What a skin cyst is
It is a benign sac with a wall of epidermal cells, which slowly fills with keratin — a thick, cheese-like material with a characteristic smell. It often has a small pore on the surface. It typically appears on the face, neck, back, scalp and trunk, and may stay stable for years.
Cyst or lipoma?
It is a fair question, since both are "lumps" under the skin. The difference:
- A cyst is more superficial, often with a visible pore, and can become inflamed or infected.
- A lipoma is deeper, softer, "slips" under the fingers and has no pore.
Both are benign; the distinction is made clinically and, where needed, with an ultrasound. For superficial pigmented lesions, see the article on moles and skin lesions.
Why it comes back
Here is the heart of the matter. A cyst is not just fluid in a cavity — it is a sac with a "living" wall. If someone simply "empties" or lances it, the wall remains and produces contents again: the cyst returns. That is why:
- "Squeezing" it at home is ineffective and raises the risk of infection.
- Simply draining an infected cyst gives temporary relief but is not definitive.
- The definitive solution = complete removal of the whole wall.
When it becomes inflamed or infected
A cyst may suddenly become red, swollen and painful — signs of inflammation or infection. At this stage:
- Do not press it or try to "burst" it yourself.
- An acute, painful infection may need drainage and, in some cases, antibiotics.
- The definitive removal is scheduled later, once the inflammation settles — the wall is then removed more completely, with less recurrence.
When removal is advised
A small, symptom-free cyst can simply be monitored. Removal is advised when it:
- Is growing or mechanically bothersome.
- Has become inflamed repeatedly.
- Sits where it rubs (collar, belt) or for cosmetic reasons.
- There is diagnostic doubt.
How removal is done
Removal is a minor procedure under local anaesthesia: through a small incision the whole cyst is removed together with its wall, so it cannot recur, and the incision is closed with stitches. The specimen is sent for histological examination. It takes a short time, is done as an outpatient, and you return to your daily life straight away.
When to see a doctor
Seek assessment if a cyst grows, has become inflamed even once, sits in a bothersome spot, or simply concerns you. And without delay if it becomes red, swollen and painful. A brief clinical examination is enough to plan the correct, definitive treatment.
What is a sebaceous cyst?
It is a benign sac under the skin, with a wall made of epidermal cells, that fills with keratin (a thick, cheese-like material). It often has a small pore on the surface and usually appears on the face, neck, back and trunk. It is harmless, but it can grow, become inflamed or get infected.
Why does a cyst come back after removal?
Because if even a fragment of the sac wall is left behind, the cyst re-forms. Emptying the contents or simply lancing it is not enough. The definitive solution is complete surgical removal of the whole wall, ideally when the cyst is not inflamed.
What do I do if the cyst becomes painful, red or swollen?
These are signs of inflammation or infection. Do not squeeze it or try to burst it yourself. See a doctor: an acute, painful infection may need drainage and antibiotics, while the definitive removal is done later, once the inflammation settles.
Does it definitely have to be removed?
Not always. A small, symptom-free cyst can simply be monitored. Removal is advised when it grows, is bothersome, has become inflamed repeatedly, for cosmetic reasons, or when there is doubt about the diagnosis.
How is it removed, and will there be a scar?
With a minor procedure under local anaesthesia: the whole cyst is removed together with its wall, through a small incision, and the specimen is sent for histological examination. The scar is usually small and depends on the size and location of the cyst.