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
Sinusitis is a common condition that can affect people of any age.
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.
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.
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.
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.
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Types of sinusitis
Sinusitis can sometimes develop quickly (over a period of a few days). It can develop after a cold or the flu. This type of sinusitis usually clears up within 12 weeks.
Sinusitis that lasts for more than 12 weeks is known as chronic sinusitis. It's less common but can sometimes last for many months.
Symptoms of sinusitis
The initial symptoms of a sinus infection are a green or yellow mucus discharge from your nose and severe facial pain around your cheeks, eyes or forehead.
Sinusitis usually occurs after an upper respiratory tract infection, such as a cold or the flu. It's often quite mild and clears up within 12 weeks.
You may also experience a high temperature and toothache if you have sinusitis.
A sinus infection that lasts longer than 12 weeks is known as chronic sinusitis.
Chronic sinusitis can occur as a result of a secondary bacterial infection or an underlying allergy. This can cause the membranes lining the nose and sinuses to become inflamed.
Common symptoms of chronic sinusitis include:
a blocked nose
a runny nose
a sinus headache
a reduced sense of smell
bad breath (halitosis)
Children with sinusitis may be irritable, breathe through their mouth and have difficulty feeding. Their speech may sound nasal (like they have a stuffy cold) because their sinuses are blocked.
Take your child to see your GP if you notice these symptoms.
Causes of sinusitis
There are a number of ways your sinuses can become inflamed and blocked, but the most common cause is a viral infection.
The most common viral infections that lead to sinusitis are cold and flu infections. These viruses can spread to the sinuses from the upper airways.
If a secondary bacterial infection develops, thick yellow or green mucus will be produced and your sinuses will become inflamed and swollen.
An infected tooth can also sometimes lead to a sinus infection.
There are a number of factors that can make your sinuses more vulnerable to infection. These include:
irritants – air pollution, smoke and chemicals, such as pesticides, disinfectants and household detergents
allergies –such as allergic rhinitis, asthma and hayfever
narrow nasal passages – this may be caused by a facial injury or nasal polyps (growths) inside the nose; if mucus builds up behind the narrowed areas it can lead to a sinus infection
cystic fibrosis – a genetic condition where thick, sticky mucus builds up within the body, increasing the risk of infection
Around two thirds of people who get sinusitis don't need to see their GP. Most cases are caused by a viral infection that often clears up on its own.
Sinusitis takes about two-and-a-half weeks to clear, which means it lasts longer than a cold.
For mild sinusitis, over-the-counter painkillers such as paracetamol and ibuprofen can be used to relieve a headache, high temperature and facial pain or tenderness.
Children under 16 years of age shouldn't take aspirin, and ibuprofen isn't recommended for people with certain health conditions, including asthma, stomach ulcers and severe heart failure.
Decongestant medication such as nasal sprays or drops may help relieve your symptoms. They're available over-the-counter from pharmacies and can help unblock your nose, allowing you to breathe more easily.
However, decongestants won't help speed up your recovery from sinusitis and shouldn't be used for more than a week at a time.
When to see your GP
See your GP if your symptoms don't improve after seven days, if they're getting worse, or if your sinusitis keeps coming back.
If you have severe or chronic (persistent) sinusitis, your treatment options will include:
steroid sprays or drops
surgery (if all other treatments have failed)
Your GP may refer you to an ear, nose and throat (ENT) specialist, who will carry out some tests to find the underlying cause of your sinusitis. Chronic sinusitis may last for several months.
Antihistamines may be recommended in cases where sinusitis is associated with an allergy.
Your GP may prescribe a course of antibiotics if your symptoms of sinusitis are severe and they haven't improved after seven days.
About a third of people with sinusitis will develop a bacterial infection that requires antibiotic treatment.
Steroid drops or sprays
Steroid drops or sprays are usually prescribed if you're diagnosed with chronic sinusitis because they can help reduce your swollen sinuses.
If your symptoms don't improve after a course of antibiotics, and you're still experiencing problems with your affected sinuses, functional endoscopic sinus surgery (FESS) may be recommended.
FESS is the most common operation for sinusitis and it can be effective in relieving the symptoms.
The procedure is usually carried out under general anaesthetic, but it can also be performed under local anaesthetic (where your nose is numbed).
During the procedure, the surgeon will insert an endoscope into your nose. This is a thin tube with a lens at one end that magnifies the inside of your nose. This will allow the surgeon to see the opening of your sinus drainage channels.
The surgeon will then either:
remove any tissues, such as nasal polyps (growths) that are blocking the affected sinus
inflate a tiny balloon inside your nose to open up the drainage passages from your sinuses (this is known as a balloon catheter dilation)
The operation will improve the drainage of your sinus and help your sinus to function properly.
The surgeon may also insert a self-dissolving implant into your sinus, which expands to hold the sinus open and deliver a steroid called mometasone directly to the sinus lining.
The ENT UK's website has more information about functional endoscopic sinus surgery.
The National Institute for Health and Care Excellence (NICE) also provides information about balloon catheter dilation for chronic sinusitis.