Sinusitis is inflammation of the lining of the sinuses, caused by a viral or bacterial infection.

The sinuses are small, air-filled cavities behind your cheekbones and forehead (see below). 

The main symptoms of sinusitis are:

• a blocked or runny nose
• facial pain and tenderness
• a high temperature (fever) of 38°C (100.4°F) or more
• a sinus headache

Read more about the symptoms of sinusitis.

Sinusitis is a common condition that can affect people of any age.

The sinuses

You have four pairs of sinuses in your head. There are pairs of sinuses:

• behind your forehead
• either side of the bridge of your nose
• behind your eyes
• behind your cheekbones

Your sinuses open up into the cavity of your nose and help control the temperature and water content of the air reaching your lungs. 

The mucus that's naturally produced by your sinuses usually drains into your nose through small channels. These channels can become blocked when the sinuses are infected and inflamed.

The sinuses behind the cheekbones (the largest ones) are most commonly affected.

What causes sinusitis?

A viral infection is the most common cause of sinusitis. It's usually the result of a cold or flu virus that spreads to the sinuses from the upper airways.

Following a cold or flu, a secondary bacterial infection can sometimes develop, causing the membranes that line the inside of the sinuses to become inflamed.

An infected tooth can also sometimes cause the sinuses to become infected.

Read more about the causes of sinusitis.

Diagnosing sinusitis

Your GP will usually be able to diagnose sinusitis from your symptoms (a blocked or runny nose with facial pain).

If you have severe or recurring sinusitis, your GP may refer you to an ear, nose and throat (ENT) specialist who will try to determine the underlying cause.

The specialist may use a piece of equipment called a nasal endoscope to examine the lining of your nose and sinus openings.

An imaging test, such as a computerised tomography (CT) scan, may also be used to find out what's causing your sinusitis.

Treating sinusitis

Around two thirds of people with sinusitis don't need to see their GP. In most cases, the viral infection clears up by itself.

Sinusitis takes about two-and-a-half weeks to clear up (longer than a cold). If you have mild sinusitis, over-the-counter painkillers and decongestants will help relieve your symptoms.

See your GP if your symptoms don't improve after seven days, if they're getting worse, or if your sinusitis keeps coming back. In such cases, antibiotics or a steroid spray or drops may be prescribed.

In cases of very severe sinusitis, surgery may be needed to improve the drainage and function of your sinuses. However, surgery will usually only be recommended if all other treatment options have failed. 

Read more about treating sinusitis.

Complications of sinusitis

Complications of sinusitis are fairly uncommon, but when they occur they tend to affect children more than adults.

If your child has had sinusitis and their eyelid or cheekbone is swollen, they may have a bacterial skin or tissue infection (cellulitis).

Take your child to see your GP if you notice these symptoms. Your child may be referred to an ENT specialist.

In severe cases of sinusitis, antibiotics are often used to control the spread of infection to nearby bone.

However, in very rare cases (about 1 in 10,000), the infection spreads to nearby bone, or the area around the eye, or to the blood or the brain.