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Scientists don't yet fully understand what causes nasal polyps. It's not clear why some people develop chronic inflammation or why ongoing inflammation triggers polyp formation in some people and not in others. The inflammation occurs in the fluid-producing lining (mucous membrane) of your nose and sinuses. There's some evidence that people who develop polyps have a different immune system response and different chemical markers in their mucous membranes than do those who don't develop polyps.

Nasal polyps can form at any age, but they're most common in young and middle-aged adults. Nasal polyps may form anywhere in your sinuses or nasal passages, but they appear most often in an area where sinuses near your eyes, nose and cheekbones all drain through winding passages into your nose (ostiomeatal complex).

Mar. 08, 2014