Is Red 40 Bad for You? What the Research Actually Says

Inflammation, hyperactivity, and other risks are there, but perhaps not at the levels you think.

About 94% of U.S. residents age 2 and older consume Red 40, the country’s most used synthetic food dye. It is an ingredient in about 14% of packaged foods and drinks in the U.S., including breakfast cereals, baked goods, bottled and canned beverages, frozen flavored desserts, pretty much anything gelatin-based (like Jell-O and puddings), and many condiments and sauces. We have likely all heard or read about the potential health risks surrounding Red 40 by now. But could an ingredient so common in so many people’s diets actually be that bad for you?

What You Should Know About Red 40

Allura Red AC, better known as Red 40, is a synthetic, petroleum-based azo food dye. Azo dyes contain an azo group that links two aromatic rings. They make up about 70% of all industrial dyes used.

While Red 40 is commonly found in candy, sugary cereals, and drinks, it also appears as a non-active coloring agent in many over-the-counter medications, cough syrups, chewable vitamins, and cosmetics. Red 40 is not only a potential issue in children’s diets; it is also common in adults’ diets.

The FDA considers the acceptable daily intake of Red 40 to be seven milligrams per kilogram of body weight, but has started an initiative to phase out synthetic dyes. PepsiCo’s October 2026 voluntary recall of 122,000 cases of Gatorade products containing food dyes not listed on their nutrition labels reflects that push.

Going Deeper on the Research

Although regulators can consider 7mg/kg of body weight per day a safe cap for Red 40 consumption, a growing body of evidence suggests many negative health effects, regardless of age, including gut inflammation, DNA damage, and “impact on colon health as a putative carcinogen.”

Synthetic food dyes have been found to be contaminated with trace amounts of benzidine, a crystalline aromatic amine classified as a Group 1 human carcinogen, associated with a higher risk of bladder cancer. These amounts are not typically measurable, and the FDA limits benzidine in food colorants to one part per billion, which is extremely small but still measurable. Still, any carcinogenic property in your food is not ideal.

A December 2022 study in Nature Communications by Yun Han Kwon et al. found that chronic exposure to Red 40 can exacerbate colitis in mice (i.e., inflammation of the colon lining). 

This was an animal study and therefore not proof of Red 40’s impact on humans, but the experiment used the acceptable daily intake of Red 40 and found a significant decrease in MUC2 mRNA levels — the gene that secretes a protective mucus layer against pathogens in the intestine — in the group exposed to Red 40. Association is not causation, and no direct causal relationship between Red 40 and colitis has been established in people.

Red 40 can also trigger allergic-type reactions in sensitive people, with symptoms like itching and rashes and, rarely, rhinoconjunctivitis or anaphylaxis. But these are uncommon — documented reactions to food dyes run well under 1% in the general population (a few percent at most in people prone to allergies), which is less than many people assume. As with the other findings, these are associations that warrant more research, not proof of cause.

On Children, Specifically

After reviewing dozens of human and animal studies, OEHHA concluded that children exposed to synthetic dyes showed associations with inattentiveness, hyperactivity, and restlessness—even where the evidence stopped short of proving cause and effect.

The 2007 Southampton trial in The Lancet found that a subset of children between ages 3 and 4 are more sensitive to synthetic food dyes and more prone to hyperactivity. Researchers gave 153 children with an average age of 3.6 years doses of food dyes equivalent to what is typically found in roughly two 56-gram servings of candy.

In the children with complete, reliable data, the dye mixes produced a small but statistically significant increase in the global hyperactivity aggregate compared with placebo.

Again, to be clear, association is not causation. A growing body of evidence suggests that children whose diets contain higher levels of synthetic food dyes are more prone to hyperactivity, and that adults are more susceptible to inflammatory diseases, though the latter is primarily shown in animal studies so far and requires human trials.

The Takeaway

None of the research suggests Red 40 has positive effects, though the exposure needed to cause adverse effects is typically much higher than what an average diet provides.

If you want to cut back on your Red 40 exposure, look for the following on the nutrition labels of packaged goods: 

• Red 40 (written in any way, including Red No. 40, FD&C Red 40, etc.)
• Allura Red
• Allura Red AC
• C.I. 16035
• C.I. Food Red 17
• 2-naphthalenesulfonic acid
• 6-hydroxy-5-((2-methoxy-5-methyl-4-sulfophenyl)azo)-
• Disodium salt
• Disodium 6-hydroxy-5-((2-methoxy-5-methyl-4-sulfophenyl)azo-2-naphthalene-sulfonate

A current trend is replacing synthetic dyes with natural ones, as the Gatorade recall shows, but the U.S. has not defined what “natural” means for food colorings. Natural dyes avoid the specific concerns tied to synthetic ones, though “natural” doesn’t automatically mean safer — and the color is usually more muted, since natural dyes are less stable.

Bottom Line

Currently, synthetic food colors are considered an unnecessary risk to your health, though research is ongoing on their effects on behavioral sensitivity in children and inflammatory complications in adults, which require human-controlled trials. If you suffer from chronic gut issues or skin sensitivity, consult a doctor regarding the potential impact a diet with high exposure to synthetic food dyes may have.

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