Uses Mometasone is used to prevent and treat seasonal and year-round allergy symptoms (such as stuffy/runny nose, itching, and sneezing). It is also used to treat certain growths in the nose (nasal polyps). Mometasone belongs to a class of drugs known as corticosteroids. It works by reducing swelling (inflammation) in the nasal passages. The dosage is based on your age, medical condition, and response to treatment. Do not increase your dose or use this drug more often or for longer than directed. Your condition will not improve any faster, and your risk of side effects will increase. Children may need to use this drug for a shorter amount of time to lower the risk of side effects. If a child is using the over-the-counter product, read the package information to see how long it may be used and when you should check with the doctor. This medication does not work right away. Some people will feel this medication working within 1 to 2 days, but it may take up to 2 weeks before the full benefit of this drug takes effect. When using mometasone to prevent seasonal allergy symptoms, you may need to start this medication 2 to 4 weeks before pollen season begins. Ask your doctor or pharmacist if you should also use other medications (such as nose drops/spray, allergy drugs taken by mouth) along with this drug until it takes full effect.