Epidermoid cyst

Also known as epidermal cyst, sebaceous cyst, carbuncle cyst or keratin cyst

Epidermoid cysts are small cysts or lumps that develop just under the skin and are usually found on the face, neck or back.

What is an epidermoid cyst?

They are usually painless, slow-growing, freely movable lumps; however, sometimes a cyst will become inflamed and tender. They usually form around a hair follicle, but can sometimes be triggered by skin trauma.

Image credit: DermNet NZ

Sebaceous cyst explained simply

Sebaceous cysts are also known as epidermal cysts, carbuncle cysts or keratin cysts. Dr Sal explains how to spot a sebaceous cyst, what causes them, where they usually pop up and more.

(Doctor Secrets, Canada, 2013)

What are the symptoms of an epidermoid cyst?

Most epidermoid cysts are small, non-painful lumps just beneath the skin. Sometimes they can grow very large over a number of years. At times, they can become infected. In this case, the lump becomes red and painful and you may need to see your doctor.

If there is uncertainty about what a lump is, you should see your doctor.

How are epidermoid cysts diagnosed?

In most cases, your doctor can diagnose this type of cyst by simply examining your skin. They tend to have a typical appearance including a small central point or opening. They sometimes contain a cheesy thick material that can be squeezed out through this tiny opening. However, a key feature of an epidermoid cyst is a layer of skin surrounding the cheesy material (called a capsule) which needs to be removed fully to prevent it reforming.

Occasionally, a biopsy may be needed to rule out other conditions. If you have multiple cysts, it may be a sign of other treatable conditions, eg, cystic acne, Gardner syndrome, Steatocystoma multiplex or other types of cysts.

How are they treated?

Epidermoid cysts aren't dangerous and, once the diagnosis has been confirmed, they can often be left alone. If they become red or swollen, you can try placing a warm moist cloth (compress) over the area.

Your doctor may be able to help if the cyst is painful or if there are cosmetic concerns. In these cases they may:

  • Inject an inflamed cyst with a steroid medicine to reduce swelling.
  • Drain the cyst with a small surgical incision. This is usually done is an abscess forms and may be combined with antibiotic treatment.
  • Surgically remove large cysts, ones that are in an awkward position or cysts that keep getting infected.

Learn more

Epidermoid and pilar cysts Patient Info, UK
Epidermoid cysts DermNet NZ
Cutaneous cysts MSD Consumer Information, NZ
Cutaneous cysts and pseudocysts DermNet NZ

Credits: Health Navigator Editorial Team. Last reviewed: 03 Oct 2022