earring problems

So I've had my ear lobes pierced for more than 10 years and I didnt wear earrings for a good 2 months and I've done it before when putting earrings back in it was fine but now when I put earrings in it burns my ears and just irritates them and I have no idea why I have a problem now. Am I sensative to certain metals now? (I put in earrings that I wore before and I never had problems) Any help would be great thanks