Severe Cough (Dry) every now and then.

My wife is suffering from severe cough(dry) since a couple of weeks now. She is coughing like a heavy smoker does every now and then though she has never smoked in her life. We have already consulted ENT doctor(Allergy Consultant) in our area and took the prescribed medicine and inhaler but don't see any improvements. We thought it could be due to some allergens at our place but now she has started coughing at her workplace too. She wears clean and washed apparels everyday. Just so you know she has a family history of being Asthmatic, however; I've never seen her condition getting this worse in the past. I think we should take second opinion. What kind of doctor we need to consult for such problem? Any help in this matter would be highly appreciated.