Hi, my son who is 2yrs old had a viral infection a few weeks ago, he had a terrible hacking cough which kept him awake at night and led to vomiting when coughing. Once he started coughing he would carry on for 30 mins. After 2 wks it was eventually getting better but in the last few days it's returned. Calpol does nothing for his cough, any suggestions on medicine to help him?