Is it just your palms? or any part of your skin that is exposed to tank water?
(or are your palms the only part that get wet?)
It seems a bit unusual that just the palms would be affected. In my experience, the skin covering the palms tends to be a bit more resistant to irritants then other areas of skin.
What critters/plants/substrate do you keep in your tank?
And do you regularly add any ferts or anything?