Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. Hypertension, cardiac disease, diabetes these are the factors that could induces the allergic cough particularly if patient is taking ACE inhibitor drug, this is a molecule give for high blood pressure, dry cough is a main side effect of this drug, beside this uncontrolled diabetes may be the cause of cough, in short underlying cause of cough matters, anti-tissue cough suppressant can be used but it may give just symptomatic relief and may not cure the cough. stop the ACE inhibitor if you are taking it, well control the diabetes on tight rule basis. Hope I have answered your query. Let me know if I can assist you further.