Red Dye No. 3 (erythrosine) and Red Dye No. 40 (Allura Red) are the two synthetic red food dyes that raise the most health concerns. Red No. 3 caused thyroid tumors in lab rats and is being pulled from the U.S. food supply, while Red No. 40 is linked to behavioral changes in children. A third red colorant, Red No. 2, was banned decades ago over cancer and reproductive toxicity concerns.
Red Dye No. 3: Banned Over Tumor Risk
Red Dye No. 3, also called erythrosine, has been used for decades in candy, cake decorations, and fruit cocktail cherries. In January 2025, the FDA announced it would revoke authorization for Red No. 3 in food and ingested drugs. The decision was triggered by the Delaney Clause, a federal law that prohibits any food additive shown to cause cancer in humans or animals, regardless of the dose.
The evidence came from two studies showing that male rats exposed to high levels of Red No. 3 developed thyroid tumors. The FDA itself has noted that the mechanism behind those tumors is specific to rats and does not occur in humans, and that typical human exposure levels are far lower than what caused effects in the animal studies. Still, the Delaney Clause leaves no room for interpretation: if an additive causes cancer in any animal at any dose, it cannot be approved. Manufacturers have until 2027 to reformulate products that currently contain it.
Red Dye No. 40: Behavioral Effects in Children
Red No. 40 is the most widely used artificial food dye in the United States. You’ll find it in sports drinks, candy, cereals, flavored snacks, and even some medications. On labels, it may appear as FD&C Red No. 40, Allura Red, Allura Red AC, E129, Food Red 17, or simply “Red 40.”
A major report from California’s Office of Environmental Health Hazard Assessment concluded that synthetic food dyes, Red 40 among them, are associated with adverse neurobehavioral outcomes in children. The evidence comes partly from “challenge studies” in which children followed a dye-free diet for several weeks and then received food or drinks containing dyes. Researchers measured behavior before and after using standardized methods, and the results showed that some children are clearly more sensitive to synthetic dyes than others.
Animal research adds detail to the picture. Studies have found that synthetic food dyes affect activity levels, memory, and learning in animals. They also cause measurable changes in neurotransmitters, the chemical messengers that carry signals between nerve cells, and even produce microscopic structural changes in brain tissue. None of this means every child who eats a red lollipop will become hyperactive, but it does suggest that children who are already prone to attention or behavioral difficulties may be more vulnerable.
Red 40 remains legal in the U.S., though California passed the California Food Safety Act in 2023, which bans several synthetic dyes (including Red No. 3) from foods sold in the state. The European Union requires foods containing Red 40 to carry a warning label stating the dye “may have an adverse effect on activity and attention in children.”
Red Dye No. 2: Banned Since 1976
Red Dye No. 2, also known as amaranth, was once the most common red food coloring in the U.S. Its safety was questioned almost as soon as the 1960 Color Additive Amendments required the FDA to prove existing dyes were safe. Over the next 15 years, the deadline for completing that safety review was postponed 14 times.
The concerns were serious. Russian studies in the early 1970s found that rats fed amaranth showed decreased fertility, fewer live births, and higher offspring mortality compared to control groups. One of those studies fed the dye to 50 rats over 33 months; 13 developed malignant tumors while none of the control rats did. The researchers described amaranth as having “carcinogenic activity of medium strength.” Separately, FDA in-house research on chick embryos showed increased mortality when exposed to Red No. 2 or its breakdown products. Another FDA study found a statistically significant increase in fetal deaths in rats given the dye during pregnancy at higher doses.
The FDA formally banned Red No. 2 in 1976. It has not been permitted in U.S. food since.
Carmine: A Natural Dye With Allergy Risks
Not all red dyes are synthetic. Carmine (also listed as cochineal extract, carminic acid, or E120) is derived from crushed cochineal insects and used in yogurt, juice, candy, and cosmetics. It’s generally considered safe for most people, but it can trigger allergic reactions in sensitive individuals, sometimes severe ones.
Documented cases include a 27-year-old woman who experienced anaphylaxis after eating a popsicle containing carmine, and a 35-year-old woman who developed hives, facial swelling, and asthma within two hours of eating a yogurt with an estimated 1.3 milligrams of carmine dye. Occupational exposure carries risks too: workers who handle carmine powder have developed asthma so severe it required emergency treatment, with one man’s lung function dropping 65% within two minutes of exposure in a test chamber.
These reactions are uncommon in the general population, but if you’ve noticed symptoms like hives, breathing difficulty, or stomach pain after eating brightly colored red foods, carmine is worth investigating. The FDA requires it to be listed by name on labels, so it won’t be hidden behind a vague term like “artificial color.”
How to Spot Red Dyes on Labels
Synthetic red dyes can appear under multiple names, which makes label reading tricky. Here are the ones to watch for:
- Red 40: FD&C Red No. 40, Allura Red, Allura Red AC, E129, Food Red 17, Red 40 Lake
- Red 3: FD&C Red No. 3, Erythrosine, E127
- Carmine: Cochineal extract, carminic acid, E120
Products marketed as “no artificial colors” may still contain carmine, since it’s classified as a natural colorant. If your concern is specifically about insect-derived ingredients or you have a known carmine allergy, check the ingredient list even on “natural” products.
Why Natural Red Replacements Aren’t Everywhere Yet
As Red No. 3 exits the market, food manufacturers are turning to plant-based alternatives like beet juice concentrate. Beets are the primary food source of betalains, the pigments responsible for their deep red color. But these natural pigments are finicky. Their color degrades with heat, light, oxygen exposure, and shifts in acidity. In storage tests, beet juice concentrate lost nearly 29% of its pigment over 12 weeks at room temperature and over 43% under warmer, more humid conditions.
Browning is another problem. Natural concentrates develop off-colors over time as sugars and other compounds react, dulling the vibrant red consumers expect. This is why many reformulated products look slightly different from their originals, and why natural-color versions of familiar snacks sometimes cost more. The technical challenges are real, but they’re driving rapid innovation in food science as more companies commit to removing synthetic dyes from their products.