Hello You didn t mention the age of your baby ,but as your doctor prescribed syrup , it means must be under 10 years . The montair LC ( montelukast+ levoceterizine ) is a combination of two antihistamine drugs and very potent for allergic patient ( as cold , cough allergy ). As far as about side effects , these are many like , sedation , congestion, dryness in mouth , dizziness , fatigue, rash drowsiness etc ,but in comparison these are minor . So this drug should be given in the evening time and very safe . You can give your baby even for 2-3 months continuously . Allergic cough relieve with this drug . When you think that your son is alright stop it , but recur , start again and stop , once relief , no side effect . Hope this will help . Hot coffee and steam inhalation also help in this type of cases.