I am a 45 year old man ,in 22 year age i had go throw diagnostic check for allergy and found that allergic with dust , smell and potato , i have taken many times common allergic treatment for relieve. but now from last 4-5 years , I have experienced that no cold and no fever ( As earlier ) but sudden dry cough attack for one or half hour ( When I came in touch with dust or smell or weather change), than I feel very dull and week, Please suggest me the medicine and preventive majors.