Blue 2 (Indigo Carmine)

Last reviewed October 18, 2026 · Evidence strength: Limited · How we grade evidence

In plain words: Blue 2 is a man-made deep-blue dye. It's less common than Blue 1 and less studied on its own. It's part of the US plan to phase out synthetic dyes by 2027. There's no proof it harms people at food levels, but if you're cutting dyes it's easy to skip.

Also listed on labels as: FD&C Blue No. 2, Blue 2 Lake, Indigo carmine, Indigotine, E132, artificial color

What is it, and why is it in food?

Blue 2, or indigo carmine, is a synthetic dye that gives a darker, navy-type blue. It's used in some candies, cereals and snack foods, often as an aluminum "lake."

What does the science say?

• What's known about Blue 2 specifically: Very little on its own. It is not among the six colors with an EU behavior warning, and the 2012 review found the behavior effect wasn't reliable in studies limited to US-approved colors.¹²
• The best trial: In a 2007 UK study, about 300 children drank juice with a mix of artificial colors plus the preservative sodium benzoate, or a look-alike placebo, without knowing which. On average, the colored drinks made both 3-year-olds and 8- to 9-year-olds a little more hyperactive. The effect was small, and because the preservative was in every test drink, the colors were not tested alone.³
• Pooling many studies: A 2012 review of the research found a small effect on parent-rated behavior. It shrank after correcting for studies that never got published, and it was not reliable in studies that used only US-approved colors. Teachers' ratings showed no clear effect, but the highest-quality studies did. The authors estimated food colors might play a part for about 8% of children with ADHD symptoms.²
• California's 2021 review: State scientists looked at 25 challenge trials. Sixteen found some link with behavior, and 13 of those were statistically significant. They said the safe-intake levels FDA set decades ago may not protect children who are sensitive.⁴
• Cancer: Research has not shown that the dyes still allowed in the US cause cancer at permitted levels. Red 3 is the exception, and that story is about a rat-only effect (see Red 3 (Erythrosine)).

What do regulators say?

• In April 2025, the US Department of Health and Human Services and FDA announced a plan to work with companies to remove petroleum-based dyes (Red 40, Yellow 5, Yellow 6, Blue 1, Blue 2 and Green 3) from the food supply by the end of 2027.⁵ That phase-out is voluntary. As of October 2026 these dyes are still legal in US food.
• FDA revoked Orange B (effective September 8, 2026), and the remaining synthetic dyes are on FDA's list of chemicals under review.⁶
• The EU allows Blue 2 (E132) without the children's activity warning.¹

Who should be careful?

• Children who seem sensitive to dyes. Blue 2 usually comes with other dyes, so a dye-free trial covers it.
• Everyone else: there's no need to panic about an occasional colored treat. The effect in studies is small on average.

How common is it in US foods?

In our check of USDA's Branded Foods database, 6,318 of 439,966 US packaged foods with an ingredient list name Blue 2 (about 1.4%, or roughly 1 in 70).⁷ It shows up most often in: candy (2,165); cookies & biscuits (1,001); popcorn, peanuts, seeds & related snacks (832); cakes, cupcakes, snack cakes (510); baking decorations & dessert toppings (272). These are label records companies sent to USDA, mostly in 2021 to 2023, so some products have changed since. Counts come from a text match of ingredient lists and are approximate.

Swaps and tips for families

• Spirulina and butterfly pea flower make natural blues.
• Choose cereals and snacks labeled "no artificial colors."
• Purple and dark-blue candies often combine Blue 2 with Red 40. Purple or black carrot colors are natural options.

Beyond the plate: related non-food exposures

The same certified dyes appear in many children's medicines, chewable vitamins, toothpaste and cosmetics. If your family is avoiding dyes, check those labels too, and ask your pharmacist about dye-free versions of medicines. Indigo carmine is also used in medicine as a diagnostic dye. That is a separate, supervised use.

Frequently asked questions

Is Blue 2 bad for you?

No research shows clear harm from Blue 2 by itself at food levels. It's part of the US voluntary phase-out, and families avoiding dyes for a sensitive child usually skip it.

Is Blue 2 allowed in Europe?

Yes, as E132, without the warning label required for six other colors.

What's the difference between Blue 1 and Blue 2?

They're different chemicals. Blue 1 is a bright sky blue and much more common. Blue 2 is a deeper indigo blue.

Related guides

• Blue 1 (Brilliant Blue)
• Red 40 (Allura Red)
• Food dyes and colors

Sources

Every source below was checked against PubMed, the publisher or the official page by our research team in October 2026.

1. Regulation (EC) No 1333/2008 on food additives, Annex V (colours that require the warning "may have an adverse effect on activity and attention in children"). Official Journal of the European Union (consolidated text), 2008. Link
2. Meta-analysis of attention-deficit/hyperactivity disorder or attention-deficit/hyperactivity disorder symptoms, restriction diet, and synthetic food color additives. Journal of the American Academy of Child and Adolescent Psychiatry, 2012. PubMed 22176942 · doi:10.1016/j.jaac.2011.10.015
3. Food additives and hyperactive behaviour in 3-year-old and 8/9-year-old children in the community: a randomised, double-blinded, placebo-controlled trial. Lancet (London, England), 2007. PubMed 17825405 · doi:10.1016/S0140-6736(07)61306-3
4. Potential impacts of synthetic food dyes on activity and attention in children: a review of the human and animal evidence (California OEHHA). Environ Health, 2022. PubMed 35484553 · doi:10.1186/s12940-022-00849-9
5. HHS/FDA press release, April 22 2025. Link
6. FDA constituent update (Orange B). Link
7. FoodData Central, Branded Foods dataset (release 2026-04-30). U.S. Department of Agriculture, Agricultural Research Service, 2026. Link

This guide is for general education. It is not medical advice and does not replace advice from your doctor, pediatrician, allergist or registered dietitian. If you think you or your child reacted to a food, talk to a health professional. Research changes; we review these pages when new evidence or rules come out. Last reviewed October 18, 2026. Spotted an error? Email [email protected].