Here's an interesting twist. A customer had her diamonds remounted in palladium about 2 1/2 years ago. She recently developed a rash when warring the ring and went to her doctor. The diagnosis was dermatitis but he also told her it would continue happening until she got her rings reset. Imagine her frustration! She was concerned she had invested in the wrong metal and I don't blame her. After all, that was what the doctor said, right?
Well, his intentions were good, but his information was incomplete. Palladium is a naturally white, pure hypoallergenic metal. There is no nickel, which frequently causes allergic reactions.
Another major reason people have skin reactions, especially with small stones in the ring, are the small openings beneath the stones that can fill with soaps, lotions, etc. and cause irritations. When hands get wet and/or the ring rubs against the finger, the matter beneath the stones gradually irritates the skin beneath the ring.
Solution: Have the ring professionally cleaned and polished and try the ring again once the finger is healed. Make certain your hands are dried well and take the ring off whenever possible to apply lotions, soaps, etc. Also, make sure the ring fits properly and is not too tight beyond the knuckle.
Also, remember the "Gold smudge mystery"? That is when your ring forms a dark smudge on your finger. That, to, is generally from material that has adhered to the surface of the ring and the rubbing on the finger causes the dark smudge. This can also occur with a change in medications.