Red 40 (Allura Red): What the Science Actually Shows

Red 40 is probably the most recognized food dye name in the US. Part of that comes from its ubiquity (it’s in an enormous range of products), and part comes from years of news coverage linking food dyes to children’s behavior.

The story is more specific than most coverage suggests. And it’s often tangled up with news about Red 3, a completely different dye that FDA banned in 2025. Untangling the two is a good place to start.

Two Different Dyes

Red 40 is Allura Red AC, also called FD&C Red No. 40. It’s a synthetic azo dye: a class of compounds defined by a specific nitrogen-nitrogen double bond (the azo group) in their molecular structure. Red 40 is made from petroleum-derived aromatic compounds. It produces a bright, stable red color that holds up well through processing and storage.

Red 3 is erythrosine, FD&C Red No. 3. It’s a xanthene dye with an entirely different chemical structure. FDA banned Red 3 from use in food in January 2025, after a court order required it to act on evidence that Red 3 causes thyroid tumors in male rats.

These two dyes share a color family and a number sequence. That’s about where the similarity ends. The FDA action on Red 3 did not ban Red 40. Confusion between them has been widespread.

What Red 40 Does

Red 40’s job is simple: make food look red.

That matters commercially. A fruit punch that looks pale pink sells less well than one that’s vibrantly red. Candy, cereal, yogurt, gelatin, and children’s snack foods all benefit from color consistency that plant pigments can’t reliably provide.

Natural red pigments like beet juice and carmine fade, bleed, and change with pH and temperature. Red 40 is stable across a wide range of food processing conditions. It’s also significantly cheaper than natural alternatives and produces a more uniform, predictable color.

This is why it’s in:

• Fruit punches, sports drinks, and sodas
• Candy (gummies, hard candy, licorice)
• Flavored gelatin (Jell-O and similar products)
• Cereal
• Fruit-flavored snacks marketed to children
• Flavored yogurt
• Some maraschino cherries
• Certain medications and vitamins

Red 40 provides no nutritional benefit. It’s purely aesthetic. That fact matters when weighing any degree of risk against benefit.

The ADHD Research

The most significant scientific event in Red 40’s history is the 2007 study by McCann et al., published in The Lancet (PMID: 17825405).

Researchers gave children either a placebo or a mixture containing six food dyes (including Red 40) plus sodium benzoate. The study was a randomized, double-blind, placebo-controlled trial, conducted in two groups: 3-year-olds and 8/9-year-olds from the general population.

The finding: children who consumed the dye-and-benzoate mixture showed statistically significant increases in hyperactive behavior, assessed by parents, teachers, and trained observers. The effect was present in both age groups.

This is a real peer-reviewed study with a solid design. The finding is legitimate.

The complications:

The study used a mixture of six dyes, not Red 40 alone. The mixture also included sodium benzoate, which has its own documented behavioral effects. It’s not possible from this study to determine whether Red 40 specifically was responsible, another dye was responsible, or the combination with sodium benzoate was the key factor.

The study was conducted in children from the general population, not just children with diagnosed ADHD. This means the effect may be most relevant to children at the higher end of normal activity levels, or to children with undiagnosed sensitivities, rather than to all children.

The effect size was modest. The authors themselves noted that the observed changes, while statistically significant, might not translate to clinically meaningful behavior changes in every child.

How Regulators Responded Differently

After the McCann study, regulators on two sides of the Atlantic reached different conclusions.

FDA convened an advisory panel in 2011. The panel concluded that the evidence didn’t support a causal link between food dyes and ADHD in the general population. FDA declined to require warning labels or restrict the dyes. The agency did commit to continued monitoring.

EFSA reviewed the evidence and reached a more cautious position. The EU now requires food products containing the six dyes studied in the Southampton research (including Red 40) to carry the label: “may have an adverse effect on activity and attention in children.” This requirement has made many EU food manufacturers reformulate using natural colorants instead.

This isn’t a case of one regulator being right and one being wrong. It reflects genuinely different regulatory philosophies about how to act on uncertain evidence. The EU required a warning. FDA required more evidence.

The Genotoxicity Question

Beyond ADHD, there’s a smaller body of research looking at whether Red 40 might damage DNA.

Some in vitro studies (in cells, not in living animals or humans) have found that Red 40 causes DNA strand breaks at high concentrations. The scientific consensus is that these concentrations are much higher than what’s reached through dietary exposure. The FDA and EFSA both reviewed this literature and concluded that genotoxicity at dietary levels hasn’t been established.

EFSA re-evaluated Allura Red AC in 2009 and set an acceptable daily intake of 7 mg/kg body weight per day. At typical dietary exposure levels, most people are below this threshold.

FDA added certified color additives, including Red 40, to its priority re-evaluation list in 2025. That review is ongoing.

The Bottom Line on Who Should Care

The caution verdict reflects a few things that are each individually modest but add up to a real basis for selectivity.

The ADHD behavioral evidence is real and peer-reviewed, even if it doesn’t establish causation definitively. The dye has no nutritional function. EU regulators thought the evidence warranted a warning label. FDA is taking another look.

For parents of children with ADHD or suspected attention concerns: an elimination trial of food dyes is a reasonable experiment. The downside of trying it is minimal.

For adults without specific concerns: the current evidence doesn’t call for urgent elimination. But Red 40 is in a lot of products specifically designed to attract children with bright colors, and choosing products without it is generally easy.

Red 40 provides nothing except color. When the choice is between a red and a non-red version of the same food, that’s a simple call.