Need some advise regarding childs cronic cough?

My 8 yr old son gets this cronic cough that starts in the fall and then comes and goes till spring. He is a very ';nasally'; and always hacking up flem. He does not have a fever and does not act sick. The dr. has said its just ';allergies'; but I just worry with him having all that junk in his lungs all the time. Could it be something else? Asthma? Does anyone else have any Ideas???..Need some advise regarding childs cronic cough?
your doctor is right, its more of an allergic form of cough which is only observed between fall n spring.Asthama can be ruled out as he is not having breathing difficulties nor he is having any wheezing ,if so your pediatrician would have advised you the meds for same(though asthama is also an allergic conditon involving the lung tubes ).The flem is nothing but the nasal discharge and the allergic throat congestion and irritatation causing hacking cough and it is not a lung condition or the lung junk as u mentioned .As for the ideas you can see changing for a couple of weeks to a warmer place may help , but this condition will go away by itself when he may be 12 yrs n above