is used to prevent asthma and exercise-induced narrowing of the muscles in the lungs. It is a prescription medicine. This medicine works by blocking the action of certain chemicals in the lungs. Airfast is also used to relieve seasonal allergies such as irritation in the eyes, a runny nose and a sore throat. This medicine works by preventing the release of certain substances from the nose, which are responsible for allergic conditions. It is also used to treat indoor and outdoor allergies that are present throughout the year A valid prescription should be available upon delivery