How do you know if you're having an allergic reaction? how do you treat it?

Allergic Reaction?: Not sure what you mean by allergic reaction. If you are referring to anaphylaxis then epinephrine is the treatment of choice, call 911. Allergic rhinitis is treated with OTC antihistamines, daily intranasal steroid or antihistamine sprays, saline rinses, etc. Allergy shots also an option. Avoidance of triggers is important but see an Allergist first to determine exactly what you are allergic to.