When i smell secondhand smoke my nose starts to run like crazy..any explantations?

i smoke every once in a while but not exsessivly

It sounds like you have a very sensitive mucus membrane. When your nose detects that you are inhaling smoke it sends a signal to the brain that tells it foreign particles are about to enter your system. Your brain in defense sends a signal back to your organs and makes them secret more mucus. The mucus flows up to your nose and tries to stop the toxins from entering your body by trapping them in its slime. Its a self defense system your body has.

you will die in three days

It's highly toxic. Stay away from it.

Some people are actually allergic to cigarette smoke. I don't know if this the case with you. I smoke but when I am exposed to second hand smoke it burns my eyes.

You are probably allergic to smoke.

You probably have an allergy. When I am around cigarette smoke, my nose and eyes do the same thing. I gradually become really congested. I try to avoid being around it, but sometimes it is hard to do. You may just have to leave when you start to smell it.

you are a hypochondriac. get therapy.