Singulair (montelukast) is a leukotriene (loo-koe-TRY-een) inhibitor. Leukotrienes are chemicals your body releases when you breathe in an allergen (such as pollen). These chemicals cause swelling in your lungs and tightening of the muscles around your airways, which can result in asthma symptoms.
Singulair is used to prevent asthma attacks in adults and children as young as 12 months old. Singulair is also used to prevent exercise-induced bronchospasm in adults and children who are at least 6 years old. Singulair is also used to treat symptoms of year-round (perennial) allergies in adults and children who are at least 6 months old. It is also used to treat symptoms of seasonal allergies in adults and children who are at least 2 years old.