When it's infected, a pilonidal cyst becomes a swollen mass (abscess). Signs and symptoms of an infected pilonidal cyst include:
- Reddening of the skin
- Drainage of pus or blood from an opening in the skin
- Foul smell from draining pus
When to see a doctor
If you notice any signs or symptoms of a pilonidal cyst, see your doctor. He or she can diagnose the condition by examining the lesion.
There is some disagreement about what causes pilonidal cysts. Most pilonidal cysts appear to be caused by loose hairs that penetrate the skin. Friction and pressure — skin rubbing against skin, tight clothing, bicycling, long periods of sitting or similar factors — force the hair down into skin. Responding to the hair as a foreign substance, the body creates a cyst around the hair.
This explanation accounts for rare cases of pilonidal cysts that occur in parts of the body other than near the tailbone. For example, barbers, dog groomers and sheep shearers have developed pilonidal cysts in the skin between fingers.
Another possible explanation is that normal stretching or motion of deep layers of skin causes the enlargement and rupture of a hair follicle, the structure from which a hair grows. A cyst then forms around the ruptured follicle.
Certain factors can make you more susceptible to developing pilonidal cysts. These include:
- Inactive lifestyle
- Occupation or sports requiring prolonged sitting
- Excess body hair
- Stiff or coarse hair
- Poor hygiene
If a chronically infected pilonidal cyst isn't treated properly, there may be a slightly increased risk of developing a type of skin cancer called squamous cell carcinoma.
To help prevent pilonidal cysts, try to:
- Keep the area clean
- Lose weight if needed
- Avoid prolonged sitting
If you've had pilonidal cysts in the past, you might want to regularly shave the area or use hair removal products to reduce the risk of recurrence.