Inflammatory growths. Nasal polyps are de novo inflammatory growth arising from the lateral wall of the nose. The histo-pathology is very different from normal nasal mucosa. The cause is still not known but bacteria, virus, fungus, allergy are possibilities. They tend to grow both into the nose and into the sinuses and eventually cause nasal obstruction and anosmia.
Enlarged tissues. Nasal polyps are enlarged tissues in the back of the nose much like tonsils and adenoids. They are usually full of lymphocytes, a type of white cell that reracts to help fight allergies and infections. They become a problem when they close off the openings to your sinuses and affect drainage or make breathing through your nose difficult. They can be treated with laser surgery or inhaled steroids.