Wot is reason of constant cold? like i got cold almost all days of yr and sneezes in bunches of 8~10 together?

Almost all days i have my one of my nostril choked up due to cold, its sorta chronic, and if i mess with my nose i get sneezes 8~10 in group. Even sometimes whn i have night out in studies i get sneezes @ 4 am and thn nose runs... its really problematic coz 8~10 sneezes in public may seem some sorta nuisance and unhygenic... plz help me wid some cure for it...