How do I know wether my face is having allergy reaction or just normal breakouts?

Several differences. Normal breakouts usually are pimples, small bumps with pus in them. Allergic reactions often involve a lot of itching and a fine sandpaper like rash. Allergic reactions also often involve some swelling of the tissues of the face. If you experience any shortness of breath this could also be an allergic reaction and you should go to hospital if this occurs.