Why does my body produce phlegm even when I am not feeling sick? When should I be concerned about the phlegm production?

Phlegm is mucus. The phlegm or mucus you secrete is normal even in a non- diseased state. Even without an illness you can produce excess mucus because of allergy - allergic rhinitis. Or you can produce it without an identifiable irritant - non-allergic rhinitis. This is a very common thing that i see patients for on a daily basis... It may just be you.