my son is suffering from coughing and wheezing on a weekly basis. his paeditrician keeps giving him the same drugs- aeroflux, histatussin, and predcort. but as soon as his meds are finished, the wheezing and coughing comes back, we tested him for milk allergies, and he tested positive, and has been on a milk free diet for three weeks. however, the coughing and wheezing continues. is it safe to give him histatussin so often?