What's The Actual Difference Between Red Dye No. 3 And No. 40?

The media buzz following the Food and Drug Administration's recent ban on red dye No. 3 in all ingestible products has caused many consumers to take a second look at what they are eating. Not only are they considering what foods contain red dye No. 3, but they are also scrutinizing products for other questionable or potentially harmful ingredients. As a result, red dye no. 40 has come into question. Though both yield a similar color, the two dyes do not have the same chemical makeup. 

Red dye No. 3 (also called red dye 3 or erythrosine) had been thought to be potentially harmful for years — the state of California banned this food additive in 2023. As such, many brands pivoted to using red dye No. 40 (also known as red dye 40 or Allura Red) instead. First registered permissible by the FDA in 1971, red dye No. 40 imparts a loud, crimson red to food products. It is one of the most prevalent dyes in food products. Both red dye 40 and red dye 3 are derived from petroleum,  but red dye 40 is also combined with aluminum to stop the dye from leaching out once it's included in a food product. 

In California, all artificial dyes, including red dye No. 40, were banned in schools in 2024, but it is still permitted at a federal level. Red dye No. 3 was banned federally, because it had been flagged as a carcinogen in rats and was also shown to cause behavioral problems in some children.

Though red dye No. 40 is considered safe to consume by the Food and Drug Administration, the production and application similarities between it and the federally banned red dye 3 raise concern for some people. In addition to being a carcinogen, red dye 3 was linked to mood and behavior conditions in children. There is a potential the same goes for red dye 40, and experts are researching that possibility. At the moment, there is minimal research to suggest that red dye 40 is also a carcinogenic additive, and only some studies have shown that red dye No. 40 possibly affects children's behavior. It also could be linked to allergic reactions and migraines. 

Red dye 40 is present in a wide range of food products, like Strawberry Pop-Tarts, Skittles, Swedish Fish candies, children's cereal, frosting, and juice drinks. It seems that the FDA is further reviewing its safety standards on all synthetic food dyes, and it remains to be seen how this will affect regulation of red dye No. 40.