You may experience some side effects while taking montelukast, though these side effects are generally mild. If you feel like this medicine may be causing you to have a side effect, please check back in with your doctor.
Common side effects may include headaches, fevers, sore throats, runny nose, sinus irritation, heartburn, and diarrhea. These side effects are usually mild and temporary. If you experience persistent or severe symptoms, contact your doctor immediately.
This is not a complete list of side effects associated with montelukast. To learn more about adverse reactions you may experience, visit the [National Institutes of Health’s DailyMed webpage].(https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=6eea668f-a2fa-447f-b2d5-4c754d13d9fa "Montelukast - National Institutes of Health’s DailyMed webpage")