After discontinuing medication due to allergic reaction, how long does it take to get out of system?

Prolonged allergy: All drugs clear your system at different rates. While many clear the bloodstream quickly along with their therapeutic effects, it only takes a tiny bit bound up in your tissues or blood to continue an allergic reaction. Also, once begun an allergic reaction may persist even after the initial cause is cleared. Because of this allergic drug reactions may last days to weeks or longer.