Nasal polyps are typically benign and consist of severely inflamed and overgrown nasal membranes (lining of the nasal cavity). Allergy may play a role in their development. A small percentage may be caused by papillomas (a type of wart) or may be premalignant or malignant (rare). Nasal polyps may be treated with medication to reduce the inflammation or to treat an underlying allergy. Surgery is reserved for cases in which medication has failed. Surgery usually involves removal of the polyps and opening the sinuses to ensure that all of the diseased tissue has been removed.