Canon has revealed that some T4i bodies may show an issue with the handgrip changing color after brief use. Not only that, but the white deposits caused by excessive use of a rubber accelerator could potentially cause an allergic reaction in very sensitive individuals. (The company is quick to note that it has not received any reports of injury or allergic reaction to date.)
The white deposit on the rubber handgrips is said to be Zinc N-N-dimethyldithiocarbamate, a compound that is sometimes used as a bactericide, disinfectant, fungicide, and insecticide. The compound isn’t actually used in the T4i’s production; instead, it’s created by a reaction of the accelerator used to speed vulcanization of the rubber handgrips. This reaction is apparently more likely to occur in high temperature, high humidity conditions.
Canon says that the problem affects some T4i bodies produced between May 31st and June 15th, 2012. These cameras have the number one as the sixth digit of the serial number; unaffected cameras have the number two or higher.
If the sixth digit of your camera is 1, enter your serial number on this page set up by Canon, and it’ll notify you whether your camera is among the affected.
If your camera is affected, Canon USA will be offering a free repair service, which will exchange the rubber grips for new ones made with the correct quantity of rubber accelerator. The service program hasn’t yet started, so Canon is asking owners of affected cameras to register their purchases.