Pilonidal sinus

Symptoms of a pilonidal sinus

A pilonidal sinus will not usually cause any noticeable symptoms unless it becomes infected.

Infection can cause a pus-filled abscess to develop.

An abscess is a painful collection of pus that causes symptoms such as:

• pain
• a tender lump under the skin
• redness of the skin
• pus draining from the sinus – the pus usually smells unpleasant
• blood draining from the sinus 
• a high temperature of 38C (100.4F) or above, although this is uncommon

These symptoms may develop quickly, often over a few days.

When to see your GP

See your GP if you think you have a pilonidal sinus.

Without treatment, any pain and infection may get worse.

Your GP should be able to diagnose a pilonidal sinus after looking at the affected area of skin.

Causes of pilonidal sinuses 

Sinuses can occur anywhere in the body. Sinus is simply a medical term for a channel or cavity.

The exact cause of a pilonidal sinus is unclear, although it's thought to be caused by loose hair piercing the skin.

Certain things can increase your chances of developing a pilonidal sinus.

These include:

• being overweight
• having a large amount of body hair
• having a job that involves a lot of sitting or driving

Pilonidal sinuses affect about 26 in 100,000 people, with at least three times as many men as women. 

Treating pilonidal sinuses

If you have a pilonidal sinus, it's important to keep the area clean and dry. It may also help to remove any hair near the sinus. These steps can reduce the risk of infection.

Showering at the end of the day to remove stray hairs from the cleft between your buttocks may also help.

If a pilonidal sinus becomes infected, it should be treated as soon as possible. This is because it’s likely to get worse.

Treatment usually involves taking antibiotics and having the pus drained from the abscess during a minor operation.

If the sinus keeps becoming infected, it may have to be surgically removed.

More useful links

• Pilonidal sinus
• How to use your health services