Canon has issued a Product Advisory for the EOS Rebel T4i (aka the EOS 650D or T6i in some markets), outlining a problem where customers may see the front rubber grips turn white after a short period of time.
This problem is isolated to a small number of units that were manufactured between May 31 and June 15, 2012, where Canon determined the cause is a chemical reaction due to a higher than normal amount of a rubber accelerator being used, which can result in a chemical reaction where Zinc bis (N,N’-dimethyldithiocarbamate) becomes deposited on the rubber grip surface.
Canon indicated that the amount of Zinc bis (N,N’-dimethyldithiocarbamate) detected during their testing of affected cameras was minimal. However, if you do have a camera where the grips are turning white, they suggest taking some precautions like washing your hands with water. You should also avoid rubbing your eyes if you’ve come in contact with the grip surfaces, because in rare cases, allergic skin reactions can occur. So, if any medical symptoms develop (for example, red eyes if you’ve rubbed them after coming in contact with the rubber grips), you should contact your physician immediately.
Canon’s Advisory on the problem contains a link to a page where you can enter in your camera’s serial number to determine if it’s affected or not, and contains more detailed information on the issue. Please see the full Canon Product Advisory by clicking here.