Red 40, also known as Allura Red AC, is a synthetic food dye made from petroleum byproducts. It’s the most widely used artificial color in the United States, added to everything from candy and soda to medications and cosmetics. It gives products a bright, cherry-red appearance that stays stable on shelves far longer than natural alternatives. The FDA has approved it for general use in foods, drugs, and cosmetics, but growing research on its health effects has made it one of the most debated food additives in recent years.
What Red 40 Is Made Of
Red 40 is classified as a sulfonated mono azo dye, which means its color comes from a specific chemical bond between nitrogen atoms. It’s synthesized from petroleum or crude oil derivatives. Early synthetic dyes were made from coal processing byproducts, earning them the name “coal-tar colors,” but modern production relies on petroleum-based raw materials. The dye is listed as E 129 on European food labels.
Where You’ll Find It
Red 40 appears in a surprisingly wide range of products. Based on the USDA’s branded food database, common sources include candy (jelly beans, gummy candies, licorice like Red Vines), fruit-flavored snacks, sodas, maraschino cherries, red chili sauces, and even smoked sausage. It’s also used in baking supplies like red sanding sugar, sprinkle mixes, and writing gels.
Beyond food, the FDA permits Red 40 in drugs and cosmetics, including products intended for use around the eyes. If you’ve ever noticed that a liquid cold medicine or a vitamin gummy is bright red, Red 40 is likely responsible.
How Your Body Processes It
Red 40 isn’t broken down by your own digestive enzymes. Instead, bacteria in your gut do the work. Specific species, including certain strains that are common in the human intestine, split the dye into two metabolites. Not all gut bacteria can break it down, though. Some common intestinal bacteria like E. coli leave it intact, while others like Fusobacterium metabolize it readily. A 2023 study in mice found that Red 40 caused DNA damage and colonic inflammation, and researchers noted that its bacterial metabolites may also be capable of damaging DNA. Whether these effects translate to humans at typical dietary levels remains an open question.
Red 40 and Children’s Behavior
The link between artificial food dyes and hyperactivity in children has been studied for decades, and the evidence points to a real but small effect. A series of landmark studies from Southampton University, each involving more than 100 children, found that mixtures containing synthetic dyes (including Red 40) produced small but statistically significant increases in hyperactivity scores compared to placebo. These effects appeared in all children, not just those with ADHD.
Two major meta-analyses help put the size of this effect in perspective. One, pooling 15 double-blind studies, found a modest effect on ADHD symptoms in parent ratings, with an effect size of 0.28. A later analysis of 24 studies calculated a slightly smaller effect size of 0.18 from parent reports, dropping to 0.12 after adjusting for potential publication bias. Attention tests given directly to children showed a somewhat larger effect size of 0.27. For context, researchers have noted this is roughly one-third the effect size of ADHD medication, equivalent to bumping a child’s hyperactivity from the 50th percentile to the 62nd.
These aren’t dramatic numbers, and teacher ratings have generally shown weaker or nonsignificant effects compared to parent ratings. But the consistency of the finding across multiple studies is what has driven regulatory action in some regions.
Safety Limits and Regulation
The FDA and the Joint Expert Committee on Food Additives have set the acceptable daily intake for Red 40 at 7 milligrams per kilogram of body weight per day. For a 150-pound adult, that works out to about 477 milligrams daily. Whether typical consumption actually approaches that limit, especially in children who eat a lot of brightly colored snacks and drinks, is a concern some researchers have raised.
In the European Union, all foods containing Red 40 must list it on the label by name or its E number (E 129). In 2024, California became the first U.S. state to ban Red 40 and five other synthetic dyes from food served in public schools, through the California School Food Safety Act signed by Governor Gavin Newsom. The law was authored by Assemblymember Jesse Gabriel. Red 40 remains fully legal in commercially sold food throughout the United States.
Allergic Reactions
True allergic reactions to food dyes are uncommon. The estimated prevalence is less than 1% in adults and 1 to 2% in children. When reactions do occur, symptoms typically begin within minutes to a few hours and can include tingling in the mouth, hives, itching, rash, and swelling. In rare severe cases, throat constriction has been reported. One documented case involved a patient who experienced throat closure within minutes of drinking a cherry-flavored Slurpee containing Red 40, and developed a facial rash after eating cupcakes colored with red food dye.
Natural Alternatives
Food manufacturers looking to replace Red 40 have several plant-based options, though none match its stability. Anthocyanins, found in berries and red vegetables, are the most studied natural red colorants, but they degrade when exposed to light, heat, and pH changes. Lycopene from tomatoes can produce comparable red tones and has been recognized in the EU as a food coloring agent. Betanin from beetroot provides pink to violet hues and is already approved as a natural additive (E-162), though it breaks down at high temperatures and in very acidic or alkaline conditions.
The central challenge with all these natural pigments is shelf life. Researchers are working on techniques like encapsulation and copigmentation to protect natural colorants from degrading, but synthetic dyes like Red 40 remain far cheaper and more reliable in processed foods. This cost and stability gap is a major reason Red 40 continues to dominate despite growing consumer demand for natural ingredients.