Nasal polyps are thought to occur as a result of inflammation in the lining (mucus membrane) of the nasal cavities and sinuses.

Inflammation causes fluid to build up in the cells of the mucus membrane. Over time, gravity pulls on the fluid-filled cells, causing them to develop into polyps.

It is unclear what triggers the process of inflammation inside the nasal cavities. However, several theories have been suggested including:

• the inflammation is a response to a bacterial, viral or fungal infection
• the inflammation is an allergic reaction – for example, to pollution
• certain genes that are inherited from your parents increases your chances of developing nasal polyps
• problems with the nervous system disrupt the normal flow of fluid through the lining of the nose, leading to inflammation
• the immune system malfunctions and attacks the tissues of the lining of the nose, causing it to become inflamed

It is possible that a combination of these factors could be responsible for nasal polyps.

Risk factors

While the exact causes of nasal polyps are unknown, several factors increase your risk of developing them. These include:

• asthma that starts in adulthood – 20-40% of people with nasal polyps also have asthma
• allergic rhinitis – where cold-like symptoms develop as a result of an allergic reaction
• cystic fibrosis – where the lungs and digestive system become clogged with a sticky fluid; about 25% people with cystic fibrosis develop nasal polyps
• having an intolerance to aspirin
• Churg-Strauss syndrome – a rare condition that causes the blood vessels to become inflamed

If you have the symptoms of nasal polyps, your GP may examine your nostrils.

If you have nasal polyps near the openings of your nostrils, they may be visible by shining a light up your nose.

However, further tests may be needed to locate polyps deeper within your nasal passageways or in one of your sinuses. 

Further testing

If further testing is required, it will usually be carried out at the ear, nose and throat (ENT) department of your local hospital.

Nasal polyps can usually be identified using a procedure called an endoscopy to examine your nasal passages.

If needed, a computerised tomography (CT) scan of your sinuses and nasal passages can also be carried out. A series of X-rays will be taken and assembled by a computer to give a more detailed image of your sinuses and nasal passages. Polyps will show up as opaque (not transparent) areas in your sinuses and the walls of your nasal passageways.

If it is thought an allergy may be contributing to your symptoms, you may be referred for an allergy skin prick test. This involves pricking your skin with tiny amounts of substances known to be common causes of allergies to see if your skin reacts.

Children

Nasal polyps are not usually found in children, with the exception of children with cystic fibrosis (where the lungs and digestive system become clogged with thick sticky mucus).

Therefore, if your child is diagnosed with nasal polyps, it is usually recommended that they are also tested for cystic fibrosis as a precaution.

A widely used test for cystic fibrosis involves measuring the amount of salt in a sample of sweat. An unusually high amount may indicate cystic fibrosis.

Read more about diagnosing cystic fibrosis.

Nasal polyps are abnormal tissue growths that grow inside the nasal passages and sinuses.

Sinuses are small, air-filled cavities found within the bones of the face. You have sinuses on either side of your nose and behind your cheekbones, eyes and forehead.

What do nasal polyps look like?

Nasal polyps vary in size. They can be yellow, grey or pink in colour. Each polyp is teardrop-shaped, and they look like grapes on a stem when fully grown.

Large nasal polyps can block your nasal passage and cause symptoms such as a blocked or runny nose and a loss of smell and taste.

These symptoms are similar to those of other conditions, such as the common cold. However, colds usually get better within 2-14 days, whereas nasal polyps do not clear up without treatment.

Read more about the symptoms of nasal polyps

What causes nasal polyps?

It is not clear what causes nasal polyps. They appear to occur as a result of inflammation (redness and swelling) inside the lining of the nasal passageways and sinuses (mucus membrane). It is not known what triggers the inflammation.

There are several factors which increase your risk of developing nasal polyps. These include:

• asthma – a long-term condition that can cause wheezing and breathlessness
• allergic rhinitis – where substances such as dust mites or animal fur cause cold-like symptoms, such as sneezing and a blocked nose 
• cystic fibrosis – a condition where the lungs and digestive system become clogged with a sticky fluid
• aspirin intolerance – where allergic-like symptoms, such as a rash, itchy skin, sneezing, a watery nose and wheezing, occur if you take aspirin; some people with an aspirin intolerance also have a similar reaction to other non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen

If nasal polyps develop in or near your sinuses, they may cause a sinus infection, resulting in your face becoming painful and tender.

Nasal polyps are not cancerous and do not increase your risk of developing nasal cancer in the future.

Read more about the causes of nasal polyps.

Diagnosing nasal polyps

Your GP will ask you about your symptoms and examine your nostrils.

If you have nasal polyps near the openings of your nostrils, they may be visible by shining a light up your nose. However, further tests may be needed to locate polyps further up your nasal passageways or in one of your sinuses.

Read more about how nasal polyps are diagnosed.

Treating nasal polyps

Nasal polyps can be treated with steroid medication (corticosteroids) to help shrink them. Corticosteroids can either be prescribed as a short course of tablets or in the form of nasal drops or spray.

Surgery is recommended for larger polyps and those that do not respond to medication. The procedure, known as endoscopic sinus surgery, is carried out using a piece of equipment called an endoscope.

The endoscope used during endoscopic sinus surgery consists of a rigid, metal tube with a camera at one end. The camera gives a clear picture of the polyps and nasal passages. The polyps are removed using tiny surgical instruments, such as a micro-debrider, which is a revolving motorised saw.

Nasal polyps usually grow back. Depending on their original size, this can take a few months or a few years after treatment with medication or surgery. People with associated conditions, such as asthma or aspirin intolerance, are more likely to have recurring polyps.

Read more about treating nasal polyps.

Nasal polyps only usually cause symptoms if an individual polyp is particularly large or if there are clusters of polyps.

The symptoms of polyps can include:

• blocked nose – which may cause breathing difficulties; you may have to breathe through your mouth
• runny nose
• mucus that drips from the back of your nose down your throat – known as post-nasal drip
• reduced sense of smell or taste – in severe cases, you may lose your sense of smell or taste completely 
• snoring 

Sinusitis

If one or more polyps develop in or around one of your sinuses, fluid and mucus can build up inside your sinus.

Sinuses are small, air-filled cavities that are located on either side of your nose, within the bones of your face.

If fluid builds up in your sinus and the polyp prevents it from draining, an infection can develop. An infection of the sinuses is known as sinusitis.

The symptoms of sinusitis include:

• facial pain and tenderness near the infected sinuses – usually a throbbing pain that feels worse when you move your head, and toothache or pain in your jaw when you eat
• a high temperature of 38°C (100.4°F) or above

Some people with nasal polyps develop repeated episodes of sinusitis.

Severe or long-term sinus infections can be very serious. If the infection spreads to your eye, it could cause your eye to swell or bulge and you may be unable to move your eye. It could also affect your vision.

Obstructive sleep apnoea (OSA)

A very large polyp or a group of polyps can temporarily block your airways while you are asleep. This condition is known as obstructive sleep apnoea (OSA).

Most people are unaware that they have breathing difficulties during the night because OSA does not cause you to wake up fully. However, constant interruptions to your sleep will mean that you feel very tired and drowsy during the day.

When to get medical help

A blocked or runny nose and a reduced sense of smell are typical symptoms of nasal polyps.

However, these symptoms are also related to several other conditions including the common cold. However, colds usually clear up within 14 days, whereas nasal polyps do not get better without treatment.

Visit your GP if you have cold-like symptoms that last for more than two weeks.

Nasal polyps can often be effectively treated with steroid medication. Surgery may be recommended for larger polyps, and for those that do not respond to medication.

Steroid sprays and drops

If you have one or more small polyps, your GP may prescribe nose drops or a nasal spray that contains steroid medicine (corticosteroids). This can reduce inflammation in your nose and shrink your polyps.

A type of spray called mometasone is usually recommended because it causes fewer side effects than other steroid sprays. The recommended dose is usually two sprays into each nostril once a day.

Most people do not experience any side effects after using mometasone. However, where side effects do occur, the most commonly reported ones are:

• headache
• sore throat
• sneezing
• nosebleeds

It can take up to five weeks of using a nasal spray before the symptoms of nasal polyps improve. If you still have symptoms after this time, you should see your GP or the specialist in charge of your care. You may require additional treatment.

If your symptoms improve, you will still need to continue using the spray long-term to reduce the chances of them returning quickly.

Steroid tablets

If you have large polyps, or if your symptoms are particularly troublesome, a short course of steroid tablets (oral corticosteroids) may be prescribed for you. They may either be prescribed for use alone or in combination with a nasal spray.

A type of steroid medication called prednisolone is usually recommended. It is likely you will be prescribed no more than 7-10 days worth of prednisolone. This is because using the medication for longer than this increases your risk of developing side effects, such as:

• weakening of your bones (osteoporosis)
• high blood pressure
• diabetes
• weight gain

If your symptoms do not improve after three weeks, you may need surgery to remove the polyps.

Surgery

Surgery to remove nasal polyps may be recommended if:

• your symptoms do not respond to steroid treatment 
• you have recurrence of nasal polyps despite treatment with steroids
• you have developed a more serious secondary condition due to the polyps, such as obstructive sleep apnoea (OSA)

If surgery is recommended to remove nasal polyps, endoscopic sinus surgery is usually used. It is carried out under general anaesthetic, usually as a day procedure.

The surgeon will pass an endoscope (a tube with a video camera at one end) into your nostrils to allow them to see inside your nose and sinuses.

Surgical instruments, such as a micro-debrider (a tiny motorised revolving saw) will be used to remove the polyps. This technique means that it is not necessary to make any cuts to your face.

Following surgery, you will be observed for about six hours. If a dressing has been used, it will be removed from your nose after a few hours. If there is no bleeding you will be discharged and allowed home to continue your recovery.

You will usually be advised to rest for two weeks after surgery, and to avoid crowds to prevent catching an infection. Your surgeon will be able to give you more detailed information and advice.

Infection at the site of the surgery and persistent nosebleeds are the most common complications of endoscopic sinus surgery. 

An infection can usually be successfully treated with antibiotics. If you have persistent nosebleeds, you should contact your surgical team because you may need to go back to hospital for further treatment.

Endoscopic sinus surgery has a good track record of success with around 90% of people reporting a marked improvement in their symptoms. However, in around 8% of cases, the polyps grow back after 2-3 years.