I have a white gold set of rings that are rhodium plated. I had the same problem, and was trying to find out what to do. I would take them off, clean them good, put triple antibiotic on my finger until it seemed to heal, then put the rings back on and the same thing would happen (a reddish rash under where the rings touched my skin). I have a ring on my right hand that this did not happen with, and I noticed that the rash was confined to the area where the diamonds were (so bacteria could have accumulated there due to moisture and caused a form of athletes foot). To test this possibility, I took off my rings (cleaned them and put them on the dresser to dry all night), put Lotrimin (athletes foot medication) around my ring finger, and put a band aid on it overnight. The next morning the rash was gone, I put my clean and dry rings, and haven't had a problem since. I hope people read this and I hope it helps.
Kristi
Hi,
This could be an callus which has formed as a result of chafing of the ring against the skin of the finger.
A callus (or callositiy) is an especially toughened area of skin which has become relatively thick and hard as a response to repeated contact or pressure.
Since repeated contact is required, calluses are most often found on hands or feet.
Treatment is to shave the calluses down, and perhaps pad them.Your doctor can pare down thickened skin or trim a large corn with a scalpel, usually during an office visit. You can apply antibiotic ointment to reduce the risk of infection.
If it is associated with itching then it could be an irritant Contact dermatitis, which requires a mild Corticosteroid ointment to be applied on the area.
ref:http://en.wikipedia.org/wiki/Callus