Two synthetic red dyes get the most scrutiny: Red 40 (Allura Red AC) and Red 3 (Erythrosine). Red 40 is by far the most widely used food dye in the United States, accounting for the largest share of all synthetic color additives in the food supply. Red 3 made headlines more recently because the FDA moved to revoke its authorization entirely. Both carry distinct health concerns, and understanding the difference helps you make informed choices at the grocery store.
Red 40: The Most Common Red Dye
Red 40, also called Allura Red AC, dominates the U.S. food coloring market. Together with two yellow dyes, it accounts for roughly 90% of all synthetic dyes used in American food. You’ll find it in candy, flavored drinks, cereals, snack cakes, frosting, flavored yogurts, and even some medications. It gives products a bright red or orange-red color.
Animal research published in Toxicology Reports found that Red 40 caused DNA damage in colon cells, triggered inflammation in the lower colon and rectum, and disrupted the gut microbiome in mice. Specifically, Red 40 reduced populations of beneficial gut bacteria while increasing bacteria linked to inflammation. These effects occurred regardless of whether the mice were eating a high-fat or low-fat diet, though a high-fat diet made some effects worse. The gut breaks Red 40 down into byproducts that may contribute to these changes.
The researchers noted that the rise in Red 40 consumption over recent decades coincides with increasing rates of early-onset colorectal cancer, though coincidence alone doesn’t prove a cause. What the mouse studies do show is a plausible biological pathway: the dye damages DNA, promotes inflammation, and alters a key tumor-suppressing gene called p53 in colon tissue.
Red 40 and Children’s Behavior
The link between artificial food colors and hyperactivity in children has been studied for decades. A large body of research, including 24 double-blind, placebo-controlled studies analyzed in a meta-review, found a small but statistically significant effect. Parents reported increased hyperactive behavior in children consuming artificial food color mixes (which typically included Red 40 alongside other dyes), with an effect size of about 0.12 to 0.2. That’s a small effect on a population level, but it appeared across all children tested, not just those already diagnosed with ADHD.
Because these studies used mixtures of several dyes rather than Red 40 alone, it’s difficult to isolate exactly how much Red 40 contributes versus other colors. Still, the evidence was strong enough for the European Union to act. Since 2010, foods sold in Europe that contain Red 40 (listed as E 129) and five other synthetic dyes must carry a warning label stating: “may have an adverse effect on activity and attention in children.”
Red 3: Banned but Still in Transition
Red 3, or Erythrosine, is a cherry-red dye historically used in candies, cake decorations, fruit-flavored snacks, and certain medications. It was already banned from cosmetics and externally applied drugs in the early 1990s after studies found it caused thyroid tumors in male rats at high doses.
In January 2025, the FDA formally moved to revoke Red 3’s authorization for use in food and ingested drugs. The agency was clear that the mechanism causing cancer in male rats involves a hormone pathway specific to rats and does not appear to occur in humans. Human exposure levels are also far lower than the doses used in those studies. However, the FDA’s hand was forced by the Delaney Clause, a 1960 law that prohibits any color additive found to cause cancer in humans or animals, with no exceptions for dose or mechanism.
California had already passed the California Food Safety Act in 2023, becoming the first state to ban Red 3 along with three other additives. That state law takes effect in 2027, giving manufacturers time to reformulate. The federal revocation follows a similar timeline, so you can expect Red 3 to gradually disappear from ingredient labels over the next couple of years.
Where These Dyes Show Up
Red 40 is remarkably widespread. It appears in products you’d expect, like red candies, fruit punch, and strawberry-flavored items, but also in less obvious places. Chocolate cake mixes, barbecue sauces, flavored oatmeal, some salad dressings, and certain medications all use it. Any processed food with an ingredient list is worth checking if you want to avoid it.
Red 3 has a narrower footprint. It tends to appear in maraschino cherries, candy hearts, certain popsicles, and cake decorating gels. As the ban takes effect, these products will either switch to Red 40, natural alternatives, or reformulate entirely.
On ingredient labels, look for “Red 40,” “Allura Red AC,” “FD&C Red No. 40,” or “E 129” for one dye, and “Red 3,” “Erythrosine,” “FD&C Red No. 3,” or “E 127” for the other.
Natural Red Dyes Are Not Risk-Free
Many manufacturers are replacing synthetic reds with natural alternatives like beet juice, cranberry extract, tomato-derived pigments, or carmine (a red pigment made from crushed cochineal insects). These are generally considered safer, but carmine deserves a note of caution.
Carmine can trigger allergic reactions ranging from hives and skin redness to swelling, breathing difficulty, and in rare cases, anaphylaxis. Over 80 cases of carmine hypersensitivity have been documented worldwide. Reactions can occur from eating, inhaling, or skin contact with the dye. For most people carmine is harmless, but if you have a history of unexplained hives or allergic reactions to red-colored foods or cosmetics, it’s worth checking labels for “carmine,” “cochineal extract,” or “E 120.”
Plant-based options like beet powder, strawberry or raspberry extracts, and pomegranate juice carry no known allergy risks comparable to carmine and are the cleanest alternatives available.
How to Reduce Your Exposure
The simplest approach is reading ingredient labels on packaged foods. Red 40 is the dye you’ll encounter most often, so if you’re trying to cut back, start there. Brightly colored cereals, candy, sports drinks, and flavored snacks are the highest-concentration sources. Choosing products labeled “no artificial colors” or those using beet juice and fruit extracts as coloring eliminates most synthetic dye exposure.
For children especially, the European warning label standard offers useful guidance. Even though the behavioral effect is small on average, reducing artificial food color intake is a low-cost change with no nutritional downside. The dyes add no flavor, no nutrients, and no preservation benefit. They exist purely for appearance.