When I first joined BC, one of my first postings was about the intervention of a nickel allergy in my life. This had been confirmed, or rather, diagnosed by two French GPs.
Anyway, about 5 months ago, I was prescribed a tube of ointment called Locoid 0,1%. It seems to have done the job, at least for me anyway. I put it on every night and also before a gig or rehearsal. It's not greasy and rubs right in.
This is only available on prescription here and I imagine it's the same in the UK. Do not try to source this without asking your GP first and of course, it may not work for you but it did for me.
Last week, I had 3 reahrsals and two long gigs over 5 days. No problems whatsoever.
Just thought I'd pass this on.