How to cure cold.it is with me for last 6months. it is fixed automatically in air conditioning but with out a.c. quite troubling.?

Cold six months: What you are describing is not a cold. Because you are better in air conditioning you may be having an allergy as air conditioning removes allergens from the air you need to see your doctor for an examination to determine the cause of your symptoms and treat you properly.

Think sinusitis: I would not confuse the presence/absence of ac... If it is location dependent... I would think allergies (mold in an old office building). Otherwise a "cold" that has been present for over 6 months is likely a chronic sinus infection. You should see your local ent. You will need a ct of the sinuses with nasal endoscopy in the clinic.

Cold vs Rhinitis: What you describe seems to be a cold induced rhinitis (inflam. Of the lining of the nasal passages) vs viral "cold" which often resolves itself within a week or progress into a bacterial infection. Some remedies that might help with chronic rhinitis include saltwater flushes (available otc) or with otc antihistamines. Consider an evaluation by an ENT to find best regimen.