When would seek immediate help if i have a verified antibiotic medication allergy?

Drug rxn/allergy : Most medication allergic reaction involve the skin and will clear with time. However drug alleries can be severe, even fatal. Seek immediate help for severe multi-system reactions (anaphylaxis), reactions affecting breathing or swelling of the airway, and/or painful involvement of mucus membranes (stevens johnson syndrome). Meds associated with allergic reaction should then be avoided. Check w doc.

Anaphylaxis: Immediate type hypersensitivity, manifest by hives and shortness of breath can be life threatening.