Nasal polyps are the result of inflammation of the mucous membranes of the nose or sinuses (the moist tissue that lines organs and body cavities such as the nose, mouth and lungs), but exactly what triggers this inflammation isn't always clear.
Nasal polyps can interfere with your breathing if they grow large enough or if they grow in a cluster. They can also reduce your sense of smell by blocking the flow of air to the sensitive areas in the roof of your nose that control smell. They can also block the holes through which mucus drains out and air flows through your sinuses to ventilate them. This blockage can lead to sinusitis.
The cause of the inflammation in your nose can be a bacterial or viral infection, an allergy, an immune system response to a fungus, or it may be unknown.
Certain conditions cause nose or sinus inflammation and so make it more likely for polyps to form. These conditions include:
rhinitis - including hay fever (seasonal allergic rhinitis) and non-allergic rhinitis,
cystic fibrosis - about 1 in 4 people with cystic fibrosis develop nasal polyps,
allergy to aspirin, and
Churg-Strauss syndrome - a rare disease that inflames your blood vessels.
Your doctor may ask you to have a CT scan (computerised tomography scan) to find out the size and exact location of any polyps, including any you may have in your sinuses.
If you have one or more small polyps your doctor may prescribe you a nasal spray or nose drops that contain steroid medicine. These can reduce the inflammation in your nose and may help shrink the polyps. They should have an effect after a few days, but it can take up to a week to notice any visible improvement. The side effects of steroid nasal sprays or drops can include nosebleeds, headache and sore throat.
If the inflammation in your nose is more severe or the polyps larger, your doctor may prescribe steroid tablets, either alone or in combination with a nasal spray. Steroid tablets are usually very effective at shrinking polyps. However, because steroids taken orally can cause serious side effects, steroid tablets are usually taken for no longer than a few weeks.
If the polyps are large, and if a steroid nasal spray or tablets have not worked, you may need to have surgery to remove them. The type of procedure depends on the size, number and location of the polyps:
Polypectomy - this procedure can be used to remove most polyps. It is performed through the nostrils, without the rest of your face being involved. Under a local or general anaesthetic, small surgical instruments are inserted into your nostrils to cut out the polyps. In some cases small pieces of bone are removed from your nose to make it less likely that the polyps will reform in the future.
Endoscopic sinus surgery -this procedure may be needed if your polyps are large, in clusters, or are seriously blocking your sinuses. The surgeon will use an endoscope - a thin, rigid tube that contains a video camera - to view inside your nose and sinuses. They will then make small incisions (cuts) to your face and insert surgical instruments to open the sinus cavities and remove any polyps.
Polyps can reappear after both surgical procedures so further surgery may be needed to remove them. Nasal polyps eventually re-grow in about half of all people who have had surgery.
If you are susceptible to recurring nasal polyps, or if you have a condition such as asthma, hay fever or chronic sinus infection that makes it likely that you will develop polyps, you may need to use a steroid nasal spray daily to help prevent your nose from becoming inflamed.