Red dye does not have a straightforward link to cancer in humans, but the answer depends on which red dye you’re asking about. Red No. 3 (erythrosine) was recently banned by the FDA because it caused thyroid tumors in male rats, though the agency itself noted that the specific mechanism behind those tumors doesn’t occur in people. Red No. 40 (Allura Red), the far more common dye in the U.S. food supply, remains approved but is drawing increased scrutiny over potential DNA damage and gut inflammation seen in animal studies.
Red 3: Why the FDA Banned It
In January 2025, the FDA announced it would revoke authorization for Red No. 3 in food and ingested drugs. The decision was based on two studies showing that male rats exposed to high levels of the dye developed thyroid cancer. Under a provision of federal law called the Delaney Clause, any food additive shown to cause cancer in humans or animals must be removed from the food supply, regardless of dose or relevance to humans.
Here’s the nuance: the FDA explicitly stated that the way Red 3 causes cancer in male rats “does not occur in humans.” The dye triggered a hormonal chain reaction specific to rat thyroid biology. So the ban was a legal obligation under the Delaney Clause, not a declaration that Red 3 poses a real cancer risk to people eating it in normal amounts. California had already passed a law in 2023 prohibiting Red 3 in food products sold in the state starting January 1, 2027. The federal ban will require food manufacturers to reformulate by January 2027 and drug manufacturers by January 2028.
Red 40: The Dye Still in Almost Everything
Red No. 40 is the most widely used red food dye in the United States. It shows up in candy, fruit-flavored snacks, drink mixes, cereals, sauces, and countless other processed foods. An FDA exposure assessment found that more than 90 percent of people across all age groups, including children ages 2 to 5, consumed at least one food containing Red 40. One study of grocery store products found that about 90 percent of child-oriented candies, fruit-flavored snacks, and drink mixes contained synthetic food dyes.
Red 40 has not been banned, but recent research is raising questions. A 2023 study published in Toxicology Reports found that Red 40 caused DNA damage, colonic inflammation, and shifts in the gut microbiome in mice. The doses used in the study were calibrated to the human acceptable daily intake (ADI) of 7 mg per kilogram of body weight, scaled up to the mouse equivalent. DNA damage appeared even at a single dose equivalent to the ADI. These are animal findings, and they haven’t been replicated in human trials, but they suggest the current safety limits may deserve another look.
Contaminants in Red Dyes
Beyond the dyes themselves, synthetic food colorings can contain trace amounts of benzidine, a known human carcinogen. The FDA limits benzidine in food colorings to 1 part per billion. However, the National Toxicology Program notes that other impurities in synthetic dyes may be metabolized into benzidine after you eat them, meaning the actual exposure could be higher than what’s measured in the dye itself. Certain yellow dyes and D&C Red No. 33 (used in cosmetics and some drugs, not typically in food) have been found to contain benzidine at levels ranging from 1 to 20 ppb.
The amounts are extremely small, and no study has directly tied benzidine contamination in food dyes to cancer cases in humans. But the fact that a recognized carcinogen is present at all, even in trace quantities, is part of why advocacy groups continue to push for stricter regulation.
What the Evidence Actually Shows
No red food dye has been directly linked to cancer in humans through epidemiological studies. The rat thyroid tumors from Red 3 involved a biological pathway that doesn’t exist in human physiology. The DNA damage and gut inflammation from Red 40 have only been documented in mice so far. Benzidine contamination exists but at levels regulators consider negligible.
That said, “no proven link in humans” is not the same as “proven safe.” The current acceptable daily intakes for these dyes were set decades ago based on older toxicology data. Some researchers and organizations, including the Center for Science in the Public Interest, argue that if the ADIs were recalculated using more recent animal and human studies (particularly those examining neurobehavioral effects in children), the limits would be significantly lower. The cancer question and the behavioral question are separate issues, but they both point to the same concern: whether the safety margins built into current regulations are wide enough.
How to Reduce Your Exposure
If you want to limit your intake of red dyes, the most effective step is reducing processed foods, particularly brightly colored snacks, candies, flavored drinks, and cereals marketed to children. Check ingredient labels for “Red 40,” “Red 3,” “Allura Red AC,” or “Erythrosine.” In the European Union, foods containing these dyes must carry a warning label about potential effects on children’s behavior, which has led many manufacturers to reformulate with natural colorants like beet juice, paprika extract, or anthocyanins from fruits.
Many U.S. brands already sell versions of their products without synthetic dyes in European markets. Some of those reformulated versions are increasingly available domestically as consumer demand shifts. Red 3 will be phased out of U.S. food entirely by 2027. Red 40, for now, remains fully legal and ubiquitous.