I've heard that mercury toxicity can result in chemical sensitivity. Could this apply to water?

When I take a bath, for example, I get red rashes. I've never known why. It happens regardless of temperature of the water. Could it be reaction to something in the water? Because of this, I don't bath every day. Shampoos etc also make me feel quite sick, so I only wash my hair with them once a week and then rinse my hair couple of times a week with water only.

Would natural shampoos etc help the problem? Do you think it might improve when I have the fillings removed?