Earring Allergy

Hey guys!! Just wanted to know if any of you know anything about earring allergy or just earring "rejection" overall. I'm just wondering because my mum has had her ears pierced for over 30 years and has somewhat recently started to "reject" them, no matter what type of earrings she has on. Whether it be nickel or even gold, her lobes always get red and hurt her a lot. Soooo if anyone knows why this happens or how she can overcome this, please do share. Thanks in advance 😊