Any condition that triggers chronic inflammation in your nasal passages or sinuses increases your risk of developing nasal polyps.  Nasal polyps often result from chronic inflammation due to asthma, recurring infections (e.g., chronic sinusitis), allergies (e.g., airborne fungi), drug sensitivity (e.g., aspirin), or certain immune disorders.  Family history may also play a role, as certain genetic variations associated with immune system function make you more likely to develop nasal polyps.