Read any of the news stories linking hyperactivity in children to food dyes and you start to get really scared about Red #40. Why so hostile, Red #40? Turns out that Red #40 is the most used dye, in terms of pounds consumed. It is approved for use in beverages, baked goods, candies, cereals, drugs, and cosmetics. The disturbing fact is that the dye has been shown to cause cancer in lab tests on mice, according to a report by the Center for Science in the Public Interest.