I have platinum rings, and didn't have any problems during preganancy, but I had to quit wearing them the last couple months of pregnancy, and when I tried to wear them again, I would get red raised itchy welts around my finger! I would leave them off, let it all heal, and try again, and it kept doing it. I even tried taking them off every time I washed bottles or dishes, in the shower, anywhere where I might get water or soap residue under the ring that might irritate. It didn't help- I still got the red welts! Finally, now 10 months later,I seem to be having better luck wearing them. Now I can wear them for a couple weeks before I start getting the red marks on my fingers, where earlier I couldn't even wear them for a day! I never took any medication or tried the nail polish thing on my rings, but I am going to take them in for a good cleaning.
So, it definitely can happen with platinum! I'm hoping in another couple months the reaction will be gone and I can wear my rings all the time!
Good luck!! It may just take time- I would give it at least a year to see if the reaction goes away!!