According to the Center for Science in the Public Interest, Red 40 and other AFCs can cause allergic reactions in some people. Research shows they can also cause hyperactivity in children and immune system tumors in mice. Red 40 contains p-Cresidine, which the U.S. Department of Health and Human Services says is “reasonably anticipated” to be a human carcinogen.
One study found that Red 40 lowers reproductive success in rats. It also reduced parental and offspring weight, decreased brain weight, and lowered chances for survival in newborn rats.