What does Red 40 do to the body? Unpacking the Controversial Food Dye

December 5, 2025 •

3 min read

According to a 2021 report by California's Office of Environmental Health Hazard Assessment, synthetic food dyes, including Red 40, are associated with adverse neurobehavioral effects in some children. The question of what does Red 40 do to the body is a subject of ongoing debate among scientists and consumers alike.

Quick Summary

Red 40, a petroleum-derived synthetic food dye, has been linked to various health concerns, including hyperactivity in sensitive children, allergic reactions, and potential DNA damage in animal studies. Regulations and consumer safety perspectives differ globally regarding its use and labeling.

Key Points

ADHD Connection: Studies suggest Red 40 can exacerbate hyperactivity and other behavioral symptoms in certain children, especially those with pre-existing ADHD.
Inflammatory Response: Animal research indicates that Red 40 can cause low-grade colonic inflammation and alter the gut microbiome.
Potential Carcinogen Contaminants: Red 40 production includes trace contaminants like benzidine, a known carcinogen, though levels are regulated by the FDA.
Allergic Reactions: Some individuals experience allergic reactions or hypersensitivity to Red 40, with symptoms ranging from hives to asthma.
Regulatory Differences: The U.S. and European Union have different approaches; the EU requires warning labels for products containing Red 40.
Synthetic Origin: Red 40 is a synthetic, petroleum-derived dye that offers no nutritional value and is often found in processed foods.

What is Red 40?

Red 40, also known as Allura Red AC or FD&C Red No. 40, is a synthetic food coloring derived from petroleum. It is widely used in foods, beverages, and cosmetics for its vibrant red hue. While the FDA considers it safe within established limits, its safety is debated, leading to varying regulations internationally.

Potential Health Effects on the Body

Research into Red 40's health effects primarily focuses on its impact on children's behavior and potential links to inflammation and cancer risk, based largely on animal studies.

Effects on Child Behavior (ADHD) Concerns about Red 40's link to hyperactivity, particularly in children with ADHD, are a major focus of research. Studies, including the 2007 Southampton study, have found an association between consuming artificial food dye mixtures and increased hyperactivity in certain children.

For sensitive children: The FDA acknowledges that while dyes don't cause ADHD, some children may be sensitive and show worsened behavioral symptoms. Many parents observe improved behavior after removing synthetic dyes.
International regulations: The European Union mandates a warning label on foods with certain artificial dyes, including Red 40, indicating potential adverse effects on activity and attention in children.

Inflammation and Digestive Health Animal studies suggest Red 40 could cause inflammation, particularly in the digestive system.

Gut microbiome impact: A 2023 study found that continuous Red 40 exposure in mice led to low-grade colonic inflammation and changes in the gut microbiome, potentially contributing to digestive issues like colitis.
Increased serotonin: The same study noted increased gut serotonin production with Red 40, which contributed to inflammation.

DNA Damage and Cancer Risk Some research links Red 40 and its byproducts to DNA damage and potential carcinogenic risks.

Contaminants: Red 40 contains trace amounts of known or suspected carcinogens like benzidine and p-cresidine. Although the FDA deems these levels safe, concerns remain.
Animal studies: Studies have shown Red 40 can cause DNA damage. Chronic inflammation from consumption may also contribute to colorectal cancer over time.

Allergic and Hypersensitivity Reactions

Red 40 can cause allergic or hypersensitivity reactions in some individuals, ranging from mild rashes to more severe symptoms.

Symptoms: Reported reactions include hives, itching, skin rashes, swelling, asthma, migraines, and gastrointestinal problems.
Severity: While rare, severe allergic reactions could potentially be life-threatening.

Comparison: Red 40 vs. Red 3

Red 40 and Red 3 (erythrosine) have different regulatory and health profiles.


Aspect	Red 40 (Allura Red AC)	Red 3 (Erythrosine)
Status in U.S.	Currently approved by FDA.	Largely banned from food, drugs, and cosmetics by FDA in 2025 due to cancer concerns.
Safety Concerns	Linked to hyperactivity, inflammation (animal studies), and potential carcinogens.	Linked to thyroid cancer in rat studies.
International Regulation	Warning label required in the European Union.	Varies by country; some have stricter rules or bans.
Origin	Derived from petroleum distillates.	Derived from petroleum.

A Note on Modern Food Production

Red 40 is a cosmetic additive with no nutritional value and is often found in ultra-processed foods linked to various health issues. Reducing Red 40 intake often means reducing consumption of high-sugar, low-nutrient foods.

Conclusion

The effects of Red 40 on the body are complex and vary based on individual sensitivity and diet. While the FDA considers it safe within limits, studies on behavioral effects in sensitive children and inflammatory potential in animals warrant caution. Growing awareness has led manufacturers to use natural alternatives. For those concerned, reducing or eliminating Red 40, which offers no nutritional benefits and is common in processed foods, is a reasonable step. Reading labels and consulting a healthcare provider for personalized advice is recommended. National Institutes of Health is a useful resource for scientific literature on food additives.

Frequently Asked Questions

For children who are sensitive to it, Red 40 can worsen symptoms of hyperactivity and attention-deficit/hyperactivity disorder (ADHD). Parents have reported behavioral improvements after removing the dye from their children's diets.

Yes, some individuals may experience allergic reactions or hypersensitivity to Red 40, including symptoms like hives, itching, skin rashes, swelling, asthma, and migraines.

The relationship between Red 40 and cancer is still under investigation, though some animal studies have shown links to DNA damage and inflammation. The dye also contains trace levels of carcinogenic contaminants, but the FDA considers these amounts safe.

The FDA maintains that Red 40 is safe for consumption when used in accordance with its guidelines. In contrast, the European Union follows a more precautionary principle, requiring warning labels for some products containing Red 40 due to concerns about hyperactivity.

To avoid Red 40, carefully read ingredient labels for 'Red 40', 'FD&C Red No. 40', or 'Allura Red AC'. Opt for organic products or those colored with natural alternatives like beet juice, paprika, or fruit juices.

Most food dyes are poorly absorbed and excreted from the body within a couple of days. However, the long-term effects of repeated exposure, particularly concerning inflammation and neurological function, are still being researched.

Red 40 and Red 3 are both petroleum-derived dyes, but Red 3 was phased out for food use by the FDA in 2025 due to stronger evidence linking it to cancer. Red 40 has different chemical properties and is still currently approved in the US.