How long does a allergic reaction from a shingle vaccine last, and ca I take allergy meds and use hydrocortisone?

Don't know. Since the Zoster vaccine has been around for about a decade, the long-term efficacy can only be ascertained by experience. Theoretically it should last a life-time but practically only time will time. Since it is a live vaccine, you need to inform your doctor about this if you are on high-dose oral steroid (not topical or inhaled steroid) before getting the vaccine. Allergy medication is fine.