Nasal polyps - Causes of nasal polyps

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