Question: What does it mean to be allergic to something?
Answer: People with allergies end up with a reaction to a substance. That substance could be many different things. That substance causes a reaction which gives you nasal congestion, stuffiness, runny nose, itchy eyes, itchy nose. And then the mucus that's produced in the nose as a reaction can drip into your throat, worsen your asthma, cause a cough, give them a whole host of symptoms that can be very irritating and could be bad enough where they end up with a rash.
They could also end up with a shutdown of their lung, and their heart -- which is anaphylactic shock. And so allergies can be really, really, really bad.