What are the side effects of singulair (montelukast) in children?

Usually none: The list of possible side effects for singulair (montelukast) is long, but most are the same symptoms kids get all the time from common illnesses, meaning kids got sick while testing the medication: headache, flu-like symptoms, stomach ache, cough, dizziness, fatigue, decreased appetite, rash, fever, itching, hives, ear infections, colds, anxiety, restlessness, tremor, sleep issues. Rarely, serious ones happen.