Montelukast is used to prevent difficulty breathing, chest tightness, wheezing and coughing caused by asthma. Montelukast is also used to prevent bronchospasm (breathing difficulties) during exercise. Montelukast is also used to treat the symptoms of seasonal (occurs only at certain times of the year), and perennial (occurs all year round) allergic rhinitis (a condition associated with sneezing and stuffy, runny or itchy nose). Montelukast is in a class of medications called leukotriene receptor antagonists (LTRAs). It works by blocking the action of substances in the body that cause the symptoms of asthma and allergic rhinitis.