A 14 year-old girl comes into the emergency room presenting with lip swelling, throat tingling and rash several minutes after stepping foot on a public bus on which someone was eating peanut butter crackers. She reports that she's had these symptoms before to peanut butter exposure.

Simple enough, right? It sounds like an allergic reaction and her trigger is the ever infamous troublemaker, the most feared of the legumes, the peanut.

But, how do we know the severity of her allergic reaction, and is it possible that our patient is in anaphylaxis? How can we tell and what are the implications of the diagnosis?