Nasal polyps are non-cancerous swellings that develop in the nasal cavity or sinuses. There are two main types - ethmoidal polyps which originate in the ethmoid sinuses, and antrochoanal polyps which arise from the maxillary sinus near its opening. Nasal polyps are caused by inflammatory sinus conditions like rhinosinusitis, or disorders like cystic fibrosis. Symptoms include nasal congestion, loss of smell, headaches and sneezing. Treatment involves medications to reduce swelling, or surgical procedures to remove the polyps. Recurrence is more common for ethmoidal polyps compared to antrochoanal polyps, which rarely reoccur if completely removed.