Allergy Vs. Disease?

Okay, so by now, you've probably figured out that i've abandoned the idea of a regular blog schedule (i can barely get a regular sleep schedule!) so, i just post when an interesting idea/question/event-from-earlier-in-the-week! this post it's a question! How do you know when something is an allergy, and when it is a disease? cause right now i either have a really bad allergy to something (normal) or a weak virus (also normal!).  it's really pissing me off not knowing!!!! GRRR!!!!! well... i'm gonna probably go and do something... maybe... BYE!