Hi Doctor My Daughter Is Having Allergic Cough .she Exposed

Hi doctor my daughter is having allergic cough .she exposed to dust last week since that time she has cough.night time it's severe.during sleeping also coughing and sometime vomiting .how many days I should give ab phylline syrup.?this medicine prescribed from India her doctor.she is 5 year old.weight 22 kg.what are all the side effects ?how many ml I can give her.and how many times a day?