Sebaceous and pilar cysts Ngā kōmaoa ā-kiri, ā-ruahuru

Sebaceous cysts can form when skin cells that would usually be shed are trapped under your skin.

Pilar cysts are similar but form in your hair follicles from the cells of hair roots.

Both types of cyst are usually surrounded by a fibrous capsule under your skin. Inside the capsule is a thick, cheese-like substance. This is soggy keratin. Keratin is made up of skin cells and is what hair is made of.

Sebaceous cysts most commonly occur when you are young or middle-aged. Men get them more than women.

Pilar cysts occur in middle age and affect women more than men.

Both sebaceous and pilar cysts are slow growing, smooth, round lumps just under your skin.

Sebaceous cysts can affect any part of your body but mostly appear on your:

• face
• neck
• chest
• upper back,

They sometimes appear on your scrotum.

Pilar cysts usually appear on your scalp. Sometimes several can form on your scalp.

The appearance of the cyst, and concern about what it is, may cause some anxiety or low mood.

Occasionally a cyst can rupture under your skin or become infected. This makes them red, inflamed and painful.

If you are concerned about a lump in your skin, have it checked by your healthcare provider. They can usually diagnose a sebaceous or pilar cyst by examining the lump under your skin. But you may need a biopsy. 

Most cysts do not cause problems, so you do not need any treatment.

But if you are concerned about the way a cyst looks or it is interfering with your everyday life, it can be removed through a minor operation using a local anaesthetic.

If you have an infected cyst, you may need antibiotics and the cyst may need to be drained.