What is the difference between red dye 40 and red dye 3 in food?

October 8, 2025 •

3 min read

In January 2025, the FDA announced a ban on the use of Red Dye 3 in food and drugs, marking a significant divergence in how it is regulated compared to Red Dye 40, which remains an approved color additive. This decision highlights key differences, prompting consumers to question: What is the difference between red dye 40 and red dye 3 in food?.

Quick Summary

Red Dye 40 is a widely used synthetic colorant, whereas Red Dye 3, recently banned by the FDA due to links with thyroid cancer in animal studies, is being phased out of food and drugs by 2027.

Key Points

FDA Ban Status: Red Dye 3 was banned by the FDA in January 2025 due to cancer links in animal studies, while Red Dye 40 remains approved.
Chemical Composition: Red Dye 3 is an iodine-based compound, differentiating it from Red Dye 40, which is an azo dye.
Health Risks: Red Dye 3 was linked to thyroid tumors in rats, while Red Dye 40 is primarily associated with hyperactivity and ADHD symptoms in sensitive children.
Regulation Discrepancies: The European Union requires a warning label on Red Dye 40 products, a measure not implemented in the U.S. for the general market.
Consumer Awareness: Due to the phase-out period, consumers must continue checking ingredient lists for both dyes to make informed purchasing decisions.
Alternative Dyes: Natural alternatives like beet juice and paprika extract are increasingly used to replace synthetic red colorants.

Both Red Dye 40 and Red Dye 3 are synthetic food colorants, but they differ in chemical structure, regulatory history, and associated health concerns. Red Dye 40 (Allura Red AC) is still widely used, while Red Dye 3 (Erythrosine) has been banned by the FDA from food and ingested drugs, effective January 2027 and January 2028 respectively. This ban follows decades of debate over its potential risks.

Chemical and Physical Distinctions

The key chemical difference lies in their composition. Both are synthetic, petroleum-derived.

Red Dye 3 (Erythrosine)

Red Dye 3 is an iodine-based compound, contributing to concerns about thyroid function. It has the formula $C{20}H{6}I{4}Na{2}O_{5}$ and contains four iodine atoms.

Red Dye 40 (Allura Red AC)

Red Dye 40 is a monoazo dye without iodine. Its formula is $C{18}H{14}N{2}Na{2}O{8}S{2}$, and it is a sodium salt of an azo dye with a more polar structure than Red Dye 3.

Regulatory History and Status

The regulatory paths for these dyes have diverged significantly in the U.S.

The story of Red Dye 3

Approved for food in 1969, Red Dye 3 was partially banned from cosmetics and topical drugs in 1990 due to animal studies linking it to thyroid cancer, based on the Delaney Clause. After a 2022 petition, the FDA completely banned its use in food and ingested drugs in January 2025, with a phase-out period until January 2027 for food and January 2028 for drugs.

The status of Red Dye 40

Red Dye 40 remains FDA-approved since the 1970s, with the agency stating it's safe within limits. However, some states like California have banned it from school foods, and the EU requires a warning label about potential effects on children's activity and attention.

Associated Health Concerns

Health concerns are a major factor in the dyes' differing regulations.

Red Dye 3 Health Concerns

Due to its iodine, Red Dye 3 has been linked to thyroid issues and, in animal studies, thyroid tumors. Some studies also suggested a link to hyperactivity in children.

Red Dye 40 Health Concerns

While the FDA is not conclusive, studies link Red Dye 40 to increased hyperactivity in sensitive children. Allergic reactions have also been reported. Concerns also exist regarding contaminants like benzidine, a known carcinogen, although the FDA considers levels safe.

Comparison Table


Feature	Red Dye 40 (Allura Red AC)	Red Dye 3 (Erythrosine)
Chemical Type	Azo dye	Iodine-based xanthene dye
Petroleum Derivative	Yes	Yes
FDA Status (as of 2025)	Approved for use in food, drugs, and cosmetics	Banned for food and ingested drugs (effective 2027)
EU Status	Approved, but requires a warning label for behavioral effects	Restricted since 1994, banned for most food uses
Key Health Concerns	Hyperactivity/ADHD in sensitive children, allergic reactions, carcinogenic contaminants	Thyroid issues and cancer (animal studies), behavioral problems
Common Food Sources	Cereals, soft drinks, condiments, candy, baked goods, snacks	Was used in maraschino cherries, candy corn, fruit snacks, beverages, some medications

Finding Dyes on Labels

Labels list certified color additives by name, such as "FD&C Red No. 40" or "Red 40 Lake" and "FD&C Red No. 3" or "Erythrosine". Red Dye 3 should disappear from food labels in the next few years due to the ban.

Alternatives to Synthetic Red Dyes

Natural alternatives are increasingly used, including beet juice, beet powder, pomegranate juice, anthocyanins, paprika extract, and carmine.

Conclusion

The primary difference between red dye 40 and red dye 3 in food lies in their regulatory status and associated health risks. Red Dye 40 remains FDA-approved despite links to behavioral issues, while Red Dye 3's connection to animal thyroid cancer led to a federal ban. This ban will require manufacturers to change product formulations and will eventually remove the dye from food and drug labels. The ongoing scrutiny of synthetic dyes is promoting greater label transparency and the adoption of natural colorants. For more details, see the official FDA Color Additives page.

Frequently Asked Questions

The FDA banned Red Dye 3 (Erythrosine) in January 2025, based on animal studies from the 1980s that linked the dye to thyroid cancer in male rats. The decision was rooted in the Delaney Clause of federal law, which prohibits the use of any color additive found to cause cancer in animals or humans.

Red Dye 40 is still approved by the FDA for use in food, though it is associated with concerns, particularly regarding hyperactivity and behavioral issues in sensitive children. Allergic reactions and potential contaminants have also been noted, but the FDA considers it safe for consumption within regulatory limits.

Red Dye 40 is commonly found in a vast array of processed foods and drinks, including soft drinks, sports drinks, condiments, candy, baked goods, cereals, and dairy products like ice cream.

Before the 2025 ban, Red Dye 3 was used in many products to give them a cherry-red color. Common sources included maraschino cherries, certain candies (like candy corn and some gummies), some fruit drinks, and specific medications.

Yes, products containing Red Dye 3 may still be available for a limited time. The FDA ban includes a phase-out period, giving manufacturers until January 2027 to reformulate food products and until January 2028 for drugs.

The FDA has not found conclusive evidence that Red Dye 40 causes cancer in humans. While some studies have identified carcinogenic contaminants like benzidine in the dye, the FDA maintains that the levels are low and within safety standards. The issue remains a subject of ongoing debate and research.

Many natural alternatives can achieve a red color, such as beet juice or powder, paprika extract, pomegranate juice, and anthocyanins from berries. Some manufacturers also use carmine, a red pigment derived from cochineal insects.