... rubber hand-grips of some models may turn white, and produce a chemical that can cause an allergic reaction. According to Canon, the chemical, zinc bis (N,N’-dimethyldithiocarbamate), is not used in the production of the camera but is a potential by-product of a chemical reaction between other substances found in the hand-grip.
That advisory sounds quite indecent, no wonder many straight shooters are switching to Nikon.
However, if you have two such bodies, you can get an easy White Balance readout.