Structural or Anatomical Causes

• Nasal Polyps - Nasal polyps occur when the connective tissue matrix that keeps the mucus membrane linings of the nose intact becomes damaged.
  
  This damaged lining (which is no longer attached to the underlying tissue) starts filling with mucus, causing it to sag and develop into a "nasal polyp". They are usually benign growths that are very resilient to surgery.
  
  Any inflammation or allergy affecting the delicate mucus membranes of the nasal passages and sinus cavities will aggravate the nasal polyps causing them to swell more and block the opening to the sinuses thereby promoting the growth of bacteria, viruses or fungi. Nasal polyps are more prevalent in middle aged men and asthmatics and appear jelly-like and opaque to white in color.

• Deviated Septum - The septum is a large cartilaginous bone dividing the right and left nostrils. Certain injuries to this part, which may be due to a broken nose, playing water polo or any other injury to the nasal area can obstruct mucus drainage and breathing and therefore lead to sinusitis. An operation may however be performed to correct a deviated septum.

• Turbinates - The nasal passages contain bony projections called turbinates whose main function is to filter and warm the air that passes through these passages. When an irritation of the nasal passages occurs, these processes become inflamed and may swell causing an obstruction of mucus flow and if left untreated lead to a sinus infection.

• Concha Bullosa - This bubble or balloon shaped structure tends to develop on the middle turbinate and can exert pressure on the adjacent tissue thereby causing irritation, sinus pain and nasal blockage. This condition is usually symptom free and may be treated by endoscopic sinus surgery in severe cases.
  

Causes of sinusitis can be broadly classified

Click on any of the following to get more information on each of the different causes

1. Inflammatory and infectious causes
2. Structural or anatomical causes
3. Behavioural or life-style related risks
4. Inherited or acquired causes
5. Environmental causes