Hello, the most likely cause of your rash is due to the chicken pox vaccine. The lesions contain contagious fluid. A susceptible person may indeed contract chicken pox from you. Current vaccination guidelines in most places of the world suggest that children complete chickenpox vaccination early in their life so they are not supposed to be affected by it. Despite that, since the cause of your rash cannot be determined after such a conversation only, you ve got to visit your doctor for further guidance. Avoid contact with anyone, particularly pregnant women. I do not consider the amoxicillin, the NSAID or allopurinol to be potential causes because amoxicillin allergy usually presents much faster (at the same day it was taken) and the same applies for NSAIDs. Allopurinol is a drug that you used for so long and we don t expect side-effects to appear all of a sudden now. Contact me again, if you d like further information. Kind Regards!