Hi welcome to Health care magic forum. I would like to know whether some doctor prescribed chymoral forte or you want to try over the counter. there are so many drugs to liquify and expel the mucous of the respiratory tract. Chymoral forte is usually used for badly effected lung tissues. Six years boy having persistant cough means he must be having either allergic cough or tuberculosis. So iadvise you to consult a pediatritian for excluding tuberculosis. allergic cough could be trachi bronchitis of the new born it starts in the early child hood like months of age. and cleared by the age of 6 or 7years of age. They wont get after that. If the cough started after the age of 3years it lasts for life, when ever he is exposed to substances allergic to him he will start coughing, and needs treatment. For these people there are drugs like montelecast and long acting steroids which will minimise the cough, or stop the cough. So i advise you to consult a physician for exact diagnosis and treatment . Wishing for a quick recovery and thanks for calling.