I have found a product 'Colorsport Skin Shield' which when applied to metal jewellery, incl gold, prevents skin irritation. It is a colorless liquid, applied sparingly with a brush and in my experience, each application lasts approx 3 months. It can be found on the net at Curezone.com

I am also allergic to metal and have the same problems that you have.
I am able to wear 925 silver for a week or so before noticing a rash and its not as severe as say the rash I get from my belt because of the higher nickle content.
I have also came to realize that I am able to wear titanium because it is one of the most hypoallergenic materials out there. Hope that helps.

Ben