What Does Red 40 Do to the Human Body?

October 24, 2025 •

4 min read

While approved by the FDA, a recent 2023 study found that continuous exposure to Red 40 harmed gut health and caused inflammation in mice. This synthetic food coloring, also known as Allura Red AC, has been the subject of controversy and concern for decades regarding its effects on the human body, particularly concerning its potential impact on neurological function and hypersensitivity reactions.

Quick Summary

Red 40, a petroleum-derived food dye, is linked to potential health issues, including hyperactivity in susceptible children and rare allergic reactions. Research also explores its connection to digestive inflammation, gut microbiome changes, and DNA damage based on animal and in vitro studies. Regulatory stances vary globally, with some requiring warning labels.

Key Points

Behavioral Changes: Some studies link Red 40 to increased hyperactivity and other neurobehavioral issues, particularly in sensitive children with or without ADHD.
Allergic Reactions: Though rare, Red 40 can cause allergic or hypersensitivity reactions, leading to symptoms like hives, itching, migraines, and swelling.
Gut Inflammation: Animal studies indicate that Red 40 can disrupt the gut microbiome and cause low-grade colonic inflammation, raising concerns about digestive health.
DNA Damage: Research has found that Red 40 can cause DNA damage in laboratory settings and animal models, and it contains trace amounts of carcinogenic contaminants.
Petroleum-Derived: Red 40 is a synthetic dye made from petroleum, contrasting with natural alternatives derived from plants or insects.
Regulation Discrepancies: While the FDA deems it safe for consumption, some European countries require a warning label about its effects on children's behavior.
Avoidance Strategy: The best way to avoid Red 40 is to read food labels, as manufacturers must list it as an ingredient, and choose natural, unprocessed foods.

What is Red 40?

Red 40, or Allura Red AC, is a synthetic food dye derived from petroleum. It is one of the most widely used food colorings in the United States, found in thousands of products to enhance or add vibrant red color. It is also known as FD&C Red No. 40 or Red 40 Lake. Despite its widespread use, it remains controversial, particularly regarding its potential health impacts on specific populations.

Behavioral Impacts: Red 40 and ADHD

One of the most debated aspects of Red 40 is its potential effect on behavior, specifically Attention Deficit Hyperactivity Disorder (ADHD) symptoms. Multiple studies, including the 2007 Southampton study and a 2021 report from California's Office of Environmental Health Hazard Assessment, have investigated this link.

Exacerbation of symptoms: Research indicates that Red 40 and other synthetic dyes may worsen hyperactivity and other neurobehavioral symptoms in some children. These effects, while often modest, have been observed in children with and without pre-existing ADHD.
Individual sensitivity: The effects of food dyes appear to be highly individual. While most children show no adverse behavioral effects, a subset, particularly those with pre-existing behavioral conditions, may be more sensitive.
How it might work: Experts hypothesize that behavioral changes could be caused by multiple factors, including hypersensitivity leading to inflammation, depletion of key minerals like zinc and iron, or chemical changes in the brain.

Allergic Reactions and Hypersensitivities

While rare, Red 40 has been known to cause allergic and hypersensitivity reactions in some individuals. These are generally not true IgE-mediated allergic reactions but rather intolerances or sensitivities.

Symptoms: Reported symptoms include skin reactions like hives and itching, swelling (especially of the face), migraines, asthma-like symptoms, and in very rare, severe cases, anaphylaxis.
Difficulty identifying: Because Red 40 is in countless processed foods, it can be difficult for people to identify it as the cause of their symptoms. Tracking food intake and corresponding symptoms is often necessary to make a connection.

Digestive Health and Inflammation

Emerging research, primarily from animal studies, has raised concerns about Red 40's impact on gut health.

Animal studies: A 2023 study showed that mice with continuous Red 40 exposure experienced altered gut microbiome composition, increased serotonin production in the gut, and low-grade colonic inflammation. This chronic inflammation is a concern due to its potential link to conditions like colorectal cancer.
Gut microbiome impact: The dye can disrupt the balance of microorganisms in the digestive tract. Changes in the microbiome can affect various body functions, including the immune system, central nervous system, and hormone regulation.

Potential for DNA Damage and Cancer

Another area of active research is the potential for Red 40 to cause DNA damage and increase cancer risk.

Contaminants: While Red 40 itself is not classified as a carcinogen, some batches have been found to contain trace amounts of known carcinogens, such as benzidine.
Animal and cell studies: In vitro studies on human colon cells and in vivo studies on mice have shown that Red 40 can cause dose-dependent DNA damage and promote inflammation in the colon.
Causation vs. correlation: It is crucial to note that while these studies raise concerns, they do not definitively prove that Red 40 causes cancer in humans. More long-term epidemiological studies are needed.

Natural vs. Synthetic Color Additives

To understand the context of Red 40, it's helpful to compare it with natural coloring alternatives.


Feature	Red 40 (Synthetic)	Natural Alternatives (e.g., Beet Juice, Annatto)
Source	Petroleum by-products	Plant, animal, or mineral sources
Purity	Requires FDA batch certification for purity	Purity depends on source and extraction method
Vibrancy	Very consistent and bright color	Color can vary; less vibrant or stable
Health Risks	Potential links to hyperactivity, allergies, inflammation, and DNA damage	Can also cause allergies (e.g., carmine from insects), but generally considered safer
Regulation	FDA-approved in US; EU requires warning label for behavioral effects	Generally considered safer and exempt from batch certification

How to Limit or Avoid Red 40

For consumers concerned about the effects of Red 40, limiting exposure is possible. The most effective method is to read ingredient labels and avoid products that list Red 40, Allura Red AC, or FD&C Red No. 40. Other names include FD&C Red no. 40 Aluminium Lake. Opting for whole, unprocessed foods naturally limits intake. For food coloring, natural sources such as beet juice, paprika extract, or fruit juices are available.

Conclusion

While the FDA maintains that Red 40 is safe for consumption within regulated limits, a growing body of scientific evidence from animal and human studies suggests potential risks. The effects appear to vary significantly among individuals, with sensitive populations, especially children with ADHD, potentially experiencing behavioral changes. Concerns also exist regarding allergic reactions and potential links to digestive issues and DNA damage based on laboratory findings. Ultimately, consumers can make informed choices by understanding the known risks and considering natural alternatives, especially for those sensitive to artificial dyes.

For more detailed scientific information on food additives, consult the National Institutes of Health.

Frequently Asked Questions

Red 40 is a synthetic food dye derived from petroleum by-products.

While not classified as a carcinogen, Red 40 may contain trace amounts of known carcinogens like benzidine, and animal studies have shown it can cause DNA damage. Conclusive evidence linking it to cancer in humans is currently lacking.

Studies suggest that Red 40 may worsen hyperactivity and other behavioral symptoms in some children, especially those sensitive to food additives. It does not cause ADHD itself.

While true IgE-mediated allergic reactions are rare, some people experience hypersensitivity reactions or intolerances to Red 40, with symptoms like hives, swelling, or migraines.

Red 40 is not banned in the European Union, but foods containing it must carry a warning label stating, 'May have an adverse effect on activity and attention in children'.

Natural alternatives to Red 40 include beet juice, paprika extract, annatto, and fruit juices like pomegranate or strawberry.

You can identify Red 40 by reading the ingredient label. It may be listed as 'Red 40,' 'Allura Red AC,' or 'FD&C Red No. 40'.