Yellow 5 and Yellow 6 are not acutely toxic, and regulatory agencies in the U.S. and Europe consider them safe at typical dietary levels. But “safe” comes with caveats. A growing body of evidence links these dyes to increased hyperactivity in some children, and they can trigger allergic-type reactions in a small subset of people, particularly those sensitive to aspirin. Neither dye has been clearly shown to cause cancer in humans or animals, but concern has been significant enough that the European Union requires warning labels on any food containing them.
What Yellow 5 and Yellow 6 Actually Are
Yellow 5 (tartrazine) and Yellow 6 (sunset yellow) are synthetic dyes made from petroleum-derived compounds. They’re approved by the FDA for use in foods, drugs, and cosmetics, and they show up in a wide range of products: brightly colored sodas like Mountain Dew, candy corn, M&Ms, Starburst, sugary cereals like Cap’N Crunch, kids’ fruit drinks like Sunny D and Kool-Aid Jammers, frozen treats like Popsicles, and pre-packaged pasta mixes.
Some sources are less obvious. Yellow 5 turns up in certain pickle brands, medicines, mouthwashes, and toothpastes. If a product has an orange, yellow, or green tint that looks a little too vivid to be natural, one or both of these dyes is often involved.
The Link to Hyperactivity in Children
The most widely cited concern is behavioral. A 2007 randomized, placebo-controlled trial published in The Lancet tested two different mixtures of synthetic food dyes (including Yellow 5 and Yellow 6) on 3-year-olds and 8/9-year-olds in the general population. Researchers measured hyperactivity using a combination of parent ratings, teacher ratings, direct observation, and computerized attention tests.
Three-year-olds who consumed one of the dye mixtures scored significantly higher on the hyperactivity scale compared to placebo, with an effect size of 0.20. When the analysis was limited to children who reliably consumed most of the test drinks, that effect size jumped to 0.32. Among 8/9-year-olds who drank at least 85% of their assigned drinks, both dye mixtures produced statistically significant increases in hyperactivity, with effect sizes of 0.12 and 0.17.
These are modest effect sizes. They don’t mean every child who eats a bag of candy will bounce off the walls. But across a population, the shift is real and measurable. It was convincing enough that the European Union acted on it directly.
How Europe and the U.S. Regulate These Dyes Differently
Since July 2010, any food or drink sold in the EU that contains Yellow 5 or Yellow 6 (along with four other synthetic dyes) must carry this warning on the label: “may have an adverse effect on activity and attention in children.” This applies to virtually all food products, with narrow exceptions for meat stamps and alcoholic drinks above 1.2% alcohol. The result is that many multinational food companies reformulated their European products with natural colorings to avoid the warning label, while continuing to use synthetic dyes in the same products sold in the U.S.
The European Food Safety Authority set an acceptable daily intake for Yellow 6 at 4 mg per kilogram of body weight per day. For a 40-pound child, that works out to roughly 72 mg daily. EFSA had previously set a more cautious temporary limit of just 1 mg/kg before raising it after reviewing additional safety data in 2014.
In the United States, the FDA still considers both dyes safe and does not require behavioral warning labels. But state-level action is accelerating. California passed AB 2316 in 2024, which prohibits schools from serving or selling foods containing synthetic dye additives linked to health harms in children, including neurobehavioral issues and hyperactivity. In January 2025, Governor Newsom issued an executive order directing state agencies to further investigate the health impacts of synthetic food dyes and recommend actions to limit harm.
Allergic Reactions and Aspirin Sensitivity
Yellow 5 can cause allergic-type reactions, though this is uncommon. The estimated prevalence of tartrazine intolerance in the general population is less than 0.12%. Symptoms can include hives (urticaria) and, less commonly, asthma-like breathing difficulty.
The risk is significantly higher if you’re sensitive to aspirin. Studies have found that roughly 24% to 31% of aspirin-sensitive patients also react to Yellow 5. In one study of 140 people with asthma who were given either aspirin or tartrazine, about 25% experienced a drop in lung function of more than 20% after exposure to one of the two substances, and there was significant cross-reactivity between them. If aspirin gives you hives or triggers breathing problems, Yellow 5 deserves extra caution.
Yellow 6 has not been associated with the same degree of cross-reactivity, though individual sensitivities to any synthetic additive are always possible.
Cancer Risk: What the Evidence Shows
Neither dye has been classified as a human carcinogen. The International Agency for Research on Cancer concluded in the 1970s that Yellow 6 did not cause cancer in mice or rats when given orally or injected under the skin. Multiple animal studies in the 1980s found Yellow 6 to be non-genotoxic, meaning it did not damage DNA in a way that would initiate cancer.
The most thorough test came from the U.S. National Toxicology Program in 1981, which ran long-term cancer bioassays in both rats and mice. Rats showed no compound-related tumors at any dose. Mice showed an increase in liver tumors at a low dose but, oddly, not at the higher dose, and the results were highly variable. The NTP concluded there was “no clear evidence of carcinogenicity” for Yellow 6 in either species. Researchers did note the presence of low levels of mutagenic impurities in some batches of the dye, likely from trace aromatic amines that can form during manufacturing, but these are controlled through purity standards.
Who Should Pay the Most Attention
For most adults eating a typical diet, Yellow 5 and Yellow 6 are unlikely to cause noticeable problems. The people with the most reason to limit exposure fall into a few specific groups.
- Children, especially young children. The behavioral evidence is strongest in this age group, and children also consume more dye relative to their body weight. Brightly colored cereals, fruit drinks, and candy are marketed directly to kids, which means their daily intake can add up quickly.
- People with aspirin sensitivity. If you react to aspirin with hives, swelling, or breathing difficulty, you have a roughly 1-in-4 chance of reacting to Yellow 5 as well.
- People with existing asthma or chronic hives. These conditions appear to increase susceptibility to tartrazine reactions, particularly when aspirin sensitivity is also present.
If you want to reduce your intake, the most effective strategy is reading ingredient labels and cutting back on highly processed, brightly colored packaged foods. In the U.S., both dyes must be listed by name on food labels. In Europe, they appear as E 102 (Yellow 5) and E 110 (Yellow 6), and the behavioral warning label makes them easy to spot.