Is Red Dye 40 Bad for You? Here’s What the Science Says

There isn’t enough research to say whether Red Dye 40 is bad for you, but some human and animal studies have demonstrated negative effects. Red food dyes, particularly Red 40 (also known as Allura Red AC, Red Dye 40 or FD&C Red No. 40), have become ubiquitous in processed foods, beverages, medications, and cosmetics. While these synthetic colorants enhance visual appeal, growing scientific evidence suggests potential health risks associated with their consumption.

In this article, we’ll review the current state of knowledge regarding red food dyes and their possible impacts on human health.

What Is Red Dye 40 Made From?

Red 40 is a synthetic red azo dye derived from petroleum. It is commonly used as food coloring to create a red color and signify particular flavors, like raspberry or strawberry. It appears in countless products including candies, sodas, cereals, baked goods, medications, and cosmetics. It’s estimated that 94% of people over 2 years old in the United States consume Red 40.

Other names for Red Dye 40 include:

• Allura Red AC
• C.I. Food Red 17
• CI 16035
• Curry Red
• E 129
• Fancy Red
• FDC Red 40
• FD&C RED NO.40
• Japan Red 40
• Red 40 Lake

Red 40 was approved by the FDA for use in food in 1971 based on animal studies and short-term studies in humans.

What Are Red Dyes Used For?

Common uses of red dyes include:

Food and Beverages:

• Enhance or restore color lost during processing.
• Ensure color uniformity from batch to batch.
• Make products visually appealing.
• Examples: Candies, sodas, fruit juices, yogurts, cereals, baked goods, sauces, processed snacks.

Medications:

• Red dyes are commonly used in liquid medications with cherry or berry flavor, and may also be used to color capsules and tablets.

Cosmetics and Personal Care Products:

• Red dyes add color to makeup and other items.
• Examples: Lipstick, blush, eyeshadow, nail polish, hair dyes, soaps.

Textiles and Fabrics: Used extensively to color clothing, upholstery, carpets, and other textiles.

• The type of dye used depends on the fiber (e.g., cotton, wool, polyester, nylon).
• Historically significant, with natural dyes like madder root being used for centuries before synthetic alternatives were developed.

Inks and Paints: Provide red color for printing inks, writing inks, artistic paints, and industrial coatings.

Plastics: Used to color various plastic items, from toys to automotive parts.

Red Dye 40 Side Effects and Health Concerns

While most research on Red 40 has been in animals, there have been concerns about the effects of long-term consumption of Red 40 on human health.

Digestive and Inflammatory Health Concerns

Recent research has raised significant concerns about the effects of Red 40 on digestive health and inflammation. A 2023 study published in Nature Communications found that continuous exposure to Red 40 harmed gut health and caused inflammation in mice. The study revealed that the dye increases serotonin production in the gut, altering the composition of microorganisms and leading to increased susceptibility to inflammation.

Supporting these findings, other researchers have demonstrated that Red 40 consumption (equivalent to the Acceptable Daily Intake of 7 mg/kg/day in humans) for 10 months leads to dysbiosis and low-grade colonic inflammation in the distal colon of mice. There was also an increase in a signaling protein called Interleukin-6 that is involved in inflammation and inducible nitric oxide synthase in the colon, a marker for inflammation.

While these effects have been primarily observed in animal models and have not yet been conclusively proven in humans, they raise serious questions about the potential long-term impacts of regular Red 40 consumption. Chronic low-grade inflammation due to Red 40 is concerning as it could potentially contribute to the development of colorectal cancer over extended periods of consumption.

Allergic Reactions

Although rare, Red 40 can cause allergic reactions. These can range from mild to life-threatening. Symptoms may include hives, asthma-like symptoms, and/or swelling.

Neurological and Behavioral Effects

Another area of concern about Red 40 involves the potential neurological impacts of synthetic food dyes. The 2007 Southampton Study found associations between the consumption of several food dyes, including Allura Red AC, and increased hyperactivity in children. Further research in animals has shown memory impairment and structural changes in the brain, even at low doses. These findings collectively raise concerns about the neurological safety of Red 40, especially for children who both consume higher amounts of artificially colored foods and have developing nervous systems.

A more recent report published in 2021 by the California Office of Environmental Health Hazard Assessment concluded that synthetic food dyes are associated with adverse neurobehavioral effects. These effects include inattentiveness, hyperactivity and restlessness in certain children.

The US FDA has stated in 2023 that they have reviewed the effects of color additives on children's behavior (including Red 40) and that while most children have no side effects from them, certain children may be sensitive to them.

DNA Damage and Cancer Risk

While Allura Red AC has not been classified as a carcinogen, it has been found to be contaminated with chemicals such as benzidine, 4-nitro-p-cresidine, and p-cresidine that are known to damage DNA. This begs the questions, does red dye 40 cause cancer? Research on the effects of Red 40 in animals has been mixed so far, and human studies are lacking. Still, experts have expressed concern over the potential effects of Allura Red AC on DNA damage in the colon.

Limitations in Current Research

While the evidence raising concerns about red dyes is substantial, important limitations in the current research should be acknowledged. Most studies demonstrating harmful effects have been conducted in animal models rather than humans. While these studies provide valuable insights, direct extrapolation to human health requires caution.

Additionally, many studies examine exposure levels that may exceed typical human consumption, though some research has specifically used doses equivalent to permitted human intake levels. Long-term epidemiological studies in humans that specifically examine red dye consumption and health outcomes are generally lacking, making it difficult to establish definitive causal relationships.

Is Red Dye 40 Banned?

Red Dye 40 is currently not banned in the US, but the U.S. Department of Health and Human Services and U.S. Food and Drug Administration announced in April 2025 a plan to phase out Red 40 and other synthetic dyes from the food supply by the end of 2026. European regulations require products containing Red Dye 40 and other artificial dyes to carry a warning label stating they may have an adverse effect on activity and attention in children.

Red Dye 40 vs. Red Dye 3

It can be easy to confuse Red Dye 40 and Red Dye 3 because the names are similar. While both are synthetic colorants derived from petroleum and used to give a vibrant red hue to foods, beverages, and other products, they differ significantly in their chemical properties, regulatory status, and associated health concerns.

Red Dye 3, also called FD&C Red No. 3 erythrosine, was banned by the FDA in 2025 based on health concerns. This decision to ban the use of Red 3 in foods, beverages, and certain medications was based on the Delaney Clause, a provision in the Federal Food, Drug, and Cosmetic Act that prohibits the approval of any food additive found to cause cancer in humans or animals. Studies in the 1980s showed that high doses of Red Dye 3 could cause thyroid cancer in male lab rats, but other studies in animals and humans did not show the same effects.

How to Avoid Red 40?

If you are looking to avoid red 40, there are some things you can do:

• Always read labels on foods and drinks: It is required for Red 40 to be listed in the ingredients, although the amount of it is not required to be disclosed.
• Avoid candy, fruit-flavored snacks, and drink mixes: These categories were found to be the highest sources of Red 40 out of all red dye 40 foods.
• Choose naturally-dyed products instead: Some products use beet juice or other natural colorings instead of synthetic dyes, and offer a natural alternative to Red Dye 40.
• Ask your pharmacist about your medication: They can tell you if Red 40 was used to color your medicine, and help you find a dye-free or naturally-dyed product instead.
• Look for "Dye-Free" or "No Artificial Colors" claims: Some products explicitly state they are free of synthetic dyes.
• Make your own: When possible, preparing meals and snacks from scratch gives you complete control over the ingredients. You can use natural food-based colorings if a recipe calls for a red hue.

Conclusion

The current body of scientific evidence raises significant concerns about the safety of synthetic red food dyes, including Red 40 (Allura Red AC). Multiple animal studies have demonstrated that this commonly used food additive may cause DNA damage, promote inflammation (especially in the digestive tract), disrupt the gut microbiome, and potentially affect neurological function. The recent regulatory action against Red 3 due to cancer concerns further highlights the evolving understanding of food dye safety.

Given these findings, consumers may wish to approach foods containing synthetic red dyes with caution, especially for children and individuals with inflammatory conditions. Until more definitive human studies are available, reducing consumption of artificially colored foods represents a prudent step, particularly given that these additives serve aesthetic rather than nutritional purposes. Future research should focus on long-term human health impacts and potential interactions with other food additives to provide a more complete picture of synthetic food dye safety.

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