Mometasone furoate nasal spray is a medication used to prevent and relieve symptoms of sneezing, runny, stuffy, or itchy nose caused by hay fever or other allergies. It is also used to treat nasal polyps (swelling of the lining of the nose) . Mometasone nasal spray is in a class of medications called corticosteroids. It works by blocking the release of certain natural substances that cause allergy symptoms. If you are using mometasone nasal spray to prevent or relieve hay fever or allergy symptoms, it is usually sprayed in each nostril once a day. If you are using mometasone nasal spray to treat nasal polyps, it is usually sprayed in each nostril once or twice daily (in the morning and evening) . It is important to use mometasone nasal spray regularly for it to work. The most common side effects are an unpleasant smell and a dry or sore nose or throat.