Hi Nithya It seems that your son has bronchial asthma. Bronchial Asthma is hyperactivity of lung to different stimuli (like - dust, pollen grains, smoke etc) that causes constriction of airways. Patient develops tightness of chest, cough, respiratory distress. Asthalin contains salbutamol - a medicine that causes dilatation of lung airways and thus relieve the respiratory distress. It is a SOS medicine and only requires at time of asthma attack (severity of symptoms). It has less side effects when given through inhalation (if possible) than given oral. Montek LC - Contains Montelukast and Levocetrizine. It is more a preventive drug for asthma and seasonal allergy. It is used for some period duration as a maintenance drug. It is not effective for acute attack. It is a very well tolerated drug and has few side effects. Side effects are - Dizziness, fatigue, fever; rash; abdominal pain, dyspepsia, dental pain, gastroenteritis; increased AST; weakness; cough, nasal congestion. Aggression, agitation, angioedema, arthralgia, bleeding tendency, bruising, cholestasis, diarrhoea, dream abnormalities, drowsiness, oedema, eosinophilia, hallucinations, hepatic eosinophilic infiltration (rare), hepatitis, hypersensitivity, hypoaesthesia, insomnia, irritability, muscle cramps, myalgia, nausea, palpitation, pancreatitis, paraesthesia, pruritus, restlessness, seizure, urticaria, vasculitis, vomiting, Anaphylaxis, Churg-Strauss syndrome. However, side effects are rarely seen in children. Montek-LC can be given (and usually given) for long term to prevent attack of asthma, seasonal allergy. Every case of asthma / seasonal allergy may need individual dosing and treatment protocol. Please consult your pediatrician for duration of treatment.