Hello Welcome in H.C.M. I have gone through your query regarding persistant cough for last 6 months. Though you have taken antibiotics and anti histaminics but no relief is there. Cosidering your symptoms and irresponsive to conservative treatment it appears as you may having any of these- 1- Pharyngitis with LPR. 2- Chronic sinusitis. 3- Bronchitis (Allergic or non allergic) 4- Chronic infection of lung parenchyma. For making correct diagnosis we should ask for various relevent question to get the information than follow a thorough examination of respiratory and cardiac system and lastly do some radiological and pathological investigations. By the co-relation of above one may make a diagnosis which may be accordingly manage. Regards.