Food Dyes

by Ashley Hamer Pritchard
May 12, 2026

Sponsor an episode!

Are the dyes in our foods slowly poisoning us? US Health and Human Services Secretary RFK Jr. says they are. EU regulators act like they are. And of course, natural food proponents on social media have been claiming they are for years.

If you’re a regular Skeptoid listener, you’ve probably already filed this under yet another chemophobia panic, right alongside MSG, aluminum, and whatever new ingredient gets clicks. That instinct is often correct — a lot of the chemicals people villainize are perfectly safe, and feared for the wrong reasons.

But food dyes are a little more complicated. There are voices out there overselling their dangers. But there’s also some decent evidence for their risks. And either way, whether removing dyes from the food system will actually improve public health is an open question.

Today on Skeptoid, we’re going to look at what the science actually says about artificial food dyes to separate the legitimate concerns from the fearmongering. We’ll dig into the studies, examine why European and American regulators landed in such different places, and figure out whether dismissing this one is actually the less skeptical position.

What Are Food Dyes, and Why Are They In Everything?

Synthetic food dyes are manmade organic compounds that don’t exist in nature and are usually manufactured from raw materials obtained from petroleum or coal. They’re used solely for visual appeal — they don’t preserve food, they don’t add flavor, and they don’t provide nutrition. The FDA currently certifies seven color additives, and that’s been scaled down considerably over the last century.

The first synthetic organic dye was discovered in 1856, and a number of similar dyes soon followed. By 1900, artificial dyes were being used in all kinds of food, drugs, and cosmetics, sometimes harmlessly, other times to hide spoiled food. Many of these colorants contained heavy metals like lead, arsenic, and mercury.

So in 1906, Congress passed the Food and Drugs Act, which banned the use of toxic or harmful colors in food. The US government began issuing approvals for food dyes it deemed safe, and by 1931, there were 15 colors approved for use in food.

In the fall of 1950, dozens of children became ill after eating Halloween candy colored with Orange No. 1. The event prompted testing of all artificial colorants and led to guidelines the FDA must use to determine whether a proposed use of a color additive is safe. It also gave us the Delaney Clause: if an additive is found to induce cancer when a human or animal ingests it or is exposed to it, it should be deemed unsafe. This will become important later.

At this point, all color additives in commercial use were put on a provisional list, which meant they could be used until either their safety was established or they were banned. That list was whittled down and by the late 1980s, we were left with the seven colors still in use today: Blue No. 1, Blue No. 2, Green No. 3, Yellow No. 5, Yellow No. 6, Red No. 3, and Red No. 40.

Europe went through its own process of tightening the list of allowable colors — but unlike the US, which considers its approved dyes safe until new data is brought to its attention, the EU would later require that every approved dye be reassessed against current science on a rolling basis. That difference in philosophy is a big part of why the two regions are in such different places today.

So what are we actually worried about with food dyes? There are two main categories: cancer, and effects on children’s behavior. Let’s take them one at a time.

The Cancer Question

In the late 1970s and early 1980s, studies found that rats fed large quantities of Red No. 3 were more likely to develop thyroid tumors than rats who didn’t consume the dye. By 1990, the FDA had banned Red No. 3 from cosmetics and drugs, but not food.

Remember the Delaney Clause — the one that says the FDA should deem any substance unsafe if it causes cancer in humans or animals? At this point, they were legally obligated to ban Red No. 3 in food, but they didn’t. It wasn’t until 2025, more than 40 years after the rat data landed on the FDA’s desk, that they finally revoked the dye’s authorization for use in food. In the press release, the FDA stressed that the cancer in these studies occurred due to a rat-specific hormonal mechanism and studies in humans and other animals didn’t show the same effects.

This is roughly the state of the research on cancer in all the colorants approved for use in food. The majority have been associated with some kind of tumor in rats or mice after they ingest heroic doses of the substance, but not enough for the FDA to consider them unsafe.

However, according to the Center for Science in the Public Interest, most of these studies were conducted by the dye manufacturers themselves, many didn’t include tests of animals in utero, and almost all evaluated the safety of individual dyes, despite the fact that most dye-containing foods contain a mixture of dyes that could have different effects together. So there could be greater cancer risks than the science shows at the moment.

Still, the bottom line is that for the general population, the cancer risk from food dyes is almost certainly very small.

The Hyperactivity Question

When we shift our focus to behavioral effects on children, things get complicated. In essence, many people claim that food dyes can cause hyperactivity. And there’s some evidence to back them up.

This hypothesis was first posed in 1973 by pediatric allergist Benjamin Feingold, who presented a paper at the annual meeting of the American Medical Association proposing that eliminating artificial colors and salicylates from children’s diets improved hyperactivity. His work was incredibly popular among the public, and his 1975 book Why Your Child Is Hyperactive became a bestseller.

But the early studies into his dye- and salicylate-free diet were inconclusive, and his work was generally criticized by the medical field.

In the following years, other researchers led studies into the effects on children’s behavior after removing synthetic food dyes from their diets. What they found was significant improvement in hyperactivity symptoms when the ingredients were removed, and worsening of behavior when they were added back — but only in some children.

The most important studies in this area happened in 2004 and 2007, published by researchers at the University of Southampton. These studies looked at more than 300 children, some preschool aged, others 8 to 9 years old, and had them spend two weeks on a diet free from dyes and preservatives, then drink juice that was either left alone or mixed with a blend of food dyes and sodium benzoate. There was a small but significant increase in hyperactivity symptoms after consuming the dyed juice, though that depended on the dose and the rater — parents were more likely to rate their child as hyperactive than psychologists were.

These studies set off a flurry of government regulations in Europe. The UK government requested that food manufacturers stop using synthetic dyes and opt for natural colors and flavors, and the EU required warning labels on foods containing any of the six dyes implicated in the studies.

The US didn’t agree. After several days of hearings, the FDA Food Advisory Committee ruled 8 to 6 against requiring warning labels, and said that more research was needed.

A Decade of Research Later

In 2022, the most comprehensive modern synthesis of the research into food dyes and hyperactivity was published. This was a review by the California Office of Environmental Health Hazard Assessment, or OEHHA. It identified 25 challenge studies, including the Southampton studies. Of those 25, 13 found a statistically significant association between food dyes and behavior — roughly half.

But as with the Southampton studies, most of these studies found small, inconsistent impacts that depended on rater, dose, and the individual child. The studies also weren’t consistent in the kind or amount of synthetic dyes that they used, so it was hard to nail down a pattern.

Something else to consider is that studies in the review that were published after 1990 were more likely to find a significant effect. This could be explained by better methods, but it could also be explained by publication bias: as the association between food dyes and hyperactivity gained popularity in media, publications likely began expecting positive results and rejecting null ones. In fact, a 2012 meta analysis highlighted in the review found evidence of this publication bias — there were too many papers with small positive effects compared to the number of papers with small negative effects. If there was no publication bias, you’d expect roughly even numbers of each.

When that meta analysis corrected for publication bias, it found that the studies on the association between hyperactivity and food dyes had a parent-report effect size of 0.12. For comparison, ADHD medication has an effect size of 0.7 to 0.9 — more than five times greater. If there is an effect, it’s not very big.

Still, there is consistent evidence that some children are more sensitive to these dyes than others, possibly due to variants in genes that affect how quickly their bodies can break down histamine. That’s a chemical involved in immune responses and, as it turns out, brain signaling. The real truth may not be that food dyes cause hyperactivity — it may be something more like, food dyes probably worsen hyperactivity in a sensitive minority, and we can’t reliably identify who that minority is in advance.

Finally, the OEHHA review also flagged the fact that the FDA’s acceptable daily intake levels for these dyes were established using older studies that didn’t even look at neurobehavioral effects like hyperactivity, and they haven’t been updated since.

The EU’s Natural Experiment — And Its Limits

The point of regulating harmful chemicals is to protect people from their harms — and since the EU announced the requirement to label any food containing one of six synthetic dyes in 2008, we can look at what happened next to see if it reduced rates of hyperactivity in children.

One thing we know for sure is that it led to a large drop in use of these dyes. Prior to 2008, these six colorants appeared in roughly 3% of packaged foods and beverages in the EU. In the 14 years after the requirement took effect, that figure consistently stayed below half a percent. Manufacturers didn’t want a warning label, so they chose to reformulate and sell dye-free versions instead. It’s worth noting that these are many of the same companies still selling dyed versions of the same products in the US.

So the regulation worked to remove dyes from the food supply. But did it have an effect on human health? Surprisingly, that study hasn’t been done. We have absolutely no idea whether it had an effect on cancer or hyperactivity in the population. The effect sizes are small enough that detecting a population-level change would require an enormous, expensive longitudinal study, but in the end, you can’t say a policy worked without measuring the result.

What to Make of This

RFK Jr. called synthetic food dyes “poisonous compounds” at an April 2025 press conference and said the US would phase them out of the food supply by the end of 2026. That deadline has already slipped — the FDA’s own tracking page now lists the end of 2027 as the target, with no public acknowledgement of the change. Some major companies have made concrete commitments to phase out these dyes, including Tyson, Campbell’s, and General Mills. Others, including Coca-Cola, Unilever, and Mondelez, have made none.

But whether companies do or don’t, it’s not clear there will be much of an effect on human health. What the evidence shows is that synthetic food dyes are probably mildly harmful for some children, possibly carcinogenic through mechanisms that may or may not translate to humans, and entirely without nutritional value. Whether that’s a case for removal is an open question.

Still, even if the evidence of harm is murky, the precautionary removal of dyes from the food supply makes some sense. That’s because the upside of keeping them is vanishingly small. They make food look more colorful — that’s it. Natural alternatives exist, and multinational manufacturers are already using them in Europe.

The question was never really whether the US could remove them. It was always whether we had enough evidence to justify it — and depending on how high you set that bar, reasonable people land in different places.

By Ashley Hamer Pritchard