It has not been determined if red dye 40 is toxic to humans. Studies have been done to determine the effects of red dye 40 on rats and mice, but there is not conclusive evidence that the dye is toxic to humans, according to Healthline.
However, in humans, studies show that red dye 40 can cause hyperactivity in children with hyperactivity disorders.
Tests done on mice show that red dye 40 can cause immune system tumors in mice. A study done on rats showed that reproduction was affected by red dye 40; the weight of both the parents and offspring was low, brain weights in the offspring were low and offspring survival rates were lower than expected, says Healthline.