There are concerns about the safety of red dye 40, a popular food dye, with some reports suggesting it may cause side effects such as hyperactivity. The FDA has rules regarding the labeling of artificial colors in food, but it is unclear if these rules have been changed or if they apply to red dye 40. The safety of food dyes in general is being questioned, with one dye, red no. 3, having been banned in the US.