Nasonex Nasal Spray contains Mometasone furoate one of a group of medicines called corticosteroids. When mometasone furoate is sprayed into the nose it can help to relieve inflammation (swelling and irritation of the nose) sneezing itching and a blocked up or runny nose. Nasonex Nasal Spray Suspension is a steroid. It gets absorbed into the cells of the inner surface of the nose and works by blocking the production of certain chemical messengers that cause inflammation (swelling) and allergies. This relieves blocked or runny nose sneezing and sinus discomfort.