A skin cyst is a fluid-filled bump lying just underneath the skin. It's common and harmless, and may just go away without treatment.

However, it can be hard to tell whether a lump is a cyst or something else that might need treatment. So, if you have any sort of lump, it's best to see your GP so it can be properly diagnosed.

You can also read our page on lumps and swellings, to get a better idea of what your lump is.

Some people confuse cysts with boils or skin abscesses. Boils and abscesses are painful collections of pus that indicate an infection. A cyst may go on to become a boil or abscess.

This page covers everything you need to know about skin cysts.

What does a cyst look like?

A skin cyst looks like round, dome-shaped bump. It's yellow or whitish, often with a small dark plug through which you might be able to squeeze out pus.

It can range in size from smaller than a pea to a few centimetres across, and grows slowly.

Skin cysts don't usually hurt, but can become tender, sore and red if they become infected. Another sign of infection is foul-smelling pus coming out of it.

Where are skin cysts found?

Epidermoid cysts (one of the main types of cyst) are commonly found on the face, neck, chest, shoulders or skin around the genitals. 

These cysts affect young and middle-aged adults, and are especially common in people with acne. They don't usually run in families.

Some cysts form around the hair follicles. These are known as pilar cysts, and it's typical to find a few of these on the scalp. Unlike epidermoid cysts, pilar cysts strongly run in families. They typically affect middle-aged adults, and women more than men. 

A cyst that forms on the eyelid is known as a chalazion, or meibomian cyst.

Why do epidermoid and pilar cysts form?

Some of the cells in the top layer of skin produce keratin, a protein that gives skin its strength and flexibility. Normally, these cells move up to the surface of the skin as they start to die, so they can be shed.

But sometimes, these cells can move deeper into your skin and multiply, forming a sac. They secrete keratin into the middle of the sac, which forms a thick, yellow paste. This can ooze out of the cyst if it is burst.

Anyone can develop a skin cyst, but you're more likely to have one if you've gone through puberty, you have a history of acne, or you have injured the skin (if you've damaged a hair follicle, for example).

Skin cysts are not contagious.

How are cysts treated?

Cysts are usually harmless. If they're small and not bothering you, they can just be left alone.

You might find it helps to hold a warm flannel against the skin, to encourage the cyst to heal and reduce any inflammation.

Don't be tempted to pop the cyst, because if it's infected, you only risk spreading the infection and if the sac is left underneath the skin, it can grow back.

If you think the cyst is infected, see your GP as you may need antibiotics.

If the cyst is bothering you – for example, it's catching on your clothes or looks unpleasant – it can be removed. Your GP will use a local anaesthetic to numb your skin, make a tiny cut in the skin, and squeeze the cyst out.

This procedure will leave a scar. Also, the cyst may still grow back at later date, especially if it was removed from the scalp or scrotum (pouch of skin containing the testicles).

Page last reviewed: 26/01/2015

Next review due: 29/04/2017