Brilliant Blue
A synthetic bright-blue petroleum-derived dye used to colour sweets, ice lollies, sports drinks and tinned peas.
Animal studies at doses a few times the permitted daily limit found disrupted blood cell counts, altered immune markers, and delayed early-life reflexes in offspring. In laboratory cell tests, combining this dye with MSG produced synergistic damage to developing nerve cells at concentrations theoretically reachable from a typical snack and drink. The US FDA is working with industry to phase it out by 2027; UK and EU regulators maintain approval.
What is it?
Brilliant Blue FCF (CI 42090) is a synthetic triarylmethane dye produced by the condensation of 2-formylbenzenesulfonic acid with a specific aniline, followed by oxidation. It exists as a disodium salt and appears as a bright blue water-soluble powder. It is petroleum-derived and structurally distinct from the azo dyes that make up the Southampton Six.
What does it do?
It dissolves readily in water and imparts a vivid, stable blue colour to foods and drinks. It is also blended with yellow dyes such as tartrazine (E102) to produce the green shade in tinned mushy peas. The dye absorbs light at around 628 nanometres. Around 95-96% of the dose passes through the gut unabsorbed and is excreted in faeces; only a small fraction enters the bloodstream.
Where you will see it
Blue and blue-raspberry flavoured sweets, ice lollies and slush drinks; confectionery such as blue Smarties and pick-and-mix gummies; sports and energy drinks; cake icings and frosting; blueberry-flavoured ice cream; tinned mushy peas (combined with yellow dyes to create the green colour); some packet soups and jellies. On a UK label it will appear as Brilliant Blue FCF or E133.
What the science says
Absorption and fate in the body
The molecule is large and highly polar, which limits how much the gut absorbs. Studies in rats found roughly 96% of an oral dose passed through unchanged and appeared in faeces within 36 hours. The small fraction that is absorbed is excreted rapidly via bile. This limited uptake is one reason regulators have not set a lower ADI based on systemic toxicity alone.
Approximately 96% of an oral dose of Brilliant Blue FCF was excreted unchanged in rat faeces within 36 hours, with only around 5% absorbed from the gastrointestinal tract.
Genotoxicity and carcinogenicity
EFSA's 2010 re-evaluation and JECFA's 2017 review both examined the available genotoxicity data and concluded the dye is not genotoxic at levels relevant to food use. Long-term rat and mouse dietary studies did not produce treatment-related tumours. The acceptable daily intake was nonetheless revised downward, from 10 to 6 mg/kg body weight per day, on the basis of a more conservative reading of chronic toxicity data in rats.
EFSA concluded that Brilliant Blue FCF is not genotoxic, and lifetime dietary studies in rats and mice did not show treatment-related carcinogenicity. The ADI was revised from 10 to 6 mg/kg body weight per day using a NOAEL of 631 mg/kg from chronic rat studies and an uncertainty factor of 100.
JECFA revised the ADI to 0-6 mg/kg body weight per day at its 84th meeting, confirming the NOAEL of 631 mg/kg from rat studies and noting that estimated dietary exposure for children at the 95th percentile (around 5 mg/kg body weight per day) sits just below the ADI.
Neurobehavioral effects in animal studies
A two-generation mouse study found statistically significant effects on early reflexes and exploratory behaviour at the highest dose tested, though the authors described the effects as limited in scope. A 2022 review of blue food colouring and ADHD symptoms in children found the evidence in humans was very sparse, with only four studies qualifying for inclusion from a search covering 20 years of literature. The review noted that animal models had shown neurobehavioral changes with Blue No. 1 at high doses.
Brilliant Blue FCF fed to mice across two generations at a dietary level of 0.72% delayed development of the surface righting reflex in offspring at postnatal day 4 and produced altered exploratory behaviour in female adults. The authors described the effects on neurobehavioral parameters as limited but statistically significant.
A systematic review found only four qualifying studies specifically examining blue food colouring and ADHD symptoms in children, concluding that research on Blue No. 1 or Blue No. 2 alone in children is very limited and that more studies are needed to describe its neurotoxicity in humans.
Synergistic nerve-cell damage in laboratory tests when combined with MSG
A 2006 cell-culture study found that Brilliant Blue FCF combined with L-glutamic acid (the active component of MSG) caused significantly greater inhibition of neurite growth than either substance alone. The concentrations used were described as theoretically achievable through consuming a typical snack and drink together. This is laboratory evidence only; it has not been tested in human trials.
Combinations of Brilliant Blue FCF with L-glutamic acid showed significant synergistic inhibition of neurite outgrowth in mouse neuroblastoma cells at concentrations the authors said were theoretically achievable from consuming a typical children's snack and drink.
Immune and blood effects in rat studies
A 90-day rat study at 1.2 mg/kg per day, a dose well below the ADI of 6 mg/kg per day, found reductions in red and white blood cell counts, haemoglobin, and platelets, as well as changes in immune markers including altered immunoglobulin levels and elevated inflammatory cytokines. The biological significance of these findings for people eating foods with E133 at typical doses is not established.
Male Wistar rats given Brilliant Blue FCF orally at 1.2 mg/kg per day for 90 days showed haematological alterations including signs of megaloblastic anaemia and thrombocytopenia, along with reduced immunoglobulins and elevated inflammatory cytokines in the spleen.
US regulatory position: voluntary phase-out agreed for 2027
In April 2025 the US Department of Health and Human Services and the FDA announced a voluntary initiative with food manufacturers to remove FD&C Blue No. 1 (Brilliant Blue FCF) and five other petroleum-based synthetic dyes from the US food supply by the end of 2027. This is not a formal regulatory ban and does not apply in the UK or EU, where the dye remains approved. California has separately legislated that Blue No. 1 must be removed from school foods by December 2027.
HHS and the FDA announced in April 2025 that they would work with industry to voluntarily eliminate FD&C Blue No. 1 and five other certified synthetic dyes from the US food supply by end of 2027, citing a broader push away from petroleum-based food colours.
Where it stands with the regulators
Who should be careful
People with known sensitivity to synthetic food dyes or who experience allergic-type reactions (skin reactions, breathing symptoms) after eating brightly coloured foods and drinks may react to this dye. It is not an allergen that must be declared under UK food law, so checking the full ingredients list for Brilliant Blue FCF or E133 is the only way to identify it. Parents choosing to limit synthetic dyes in children's diets should look for E133 or Brilliant Blue FCF on the label.
The honest read
E133 has been in the food supply for decades and both EFSA and JECFA maintain current approval with a set ADI. The science picture is not clean, however. The ADI was cut from 10 to 6 mg/kg body weight per day between 1984 and 2010 on the back of new chronic-toxicity data. Animal studies have produced neurobehavioral changes in offspring and immune disruption in rats at doses below the ADI. A 2006 laboratory study found that combining this dye with MSG damaged developing nerve cells more than either substance alone, at concentrations described as achievable from a typical children's snack and drink. The US FDA is pursuing a voluntary phase-out by 2027, citing a broader move away from petroleum-based dyes, though this is not a formal ban and does not bind UK or EU manufacturers. Exposure estimates for children at the 95th percentile sit close to the ADI. The debate around synthetic food dyes is live; the picture for E133 specifically is less studied than for some of the Southampton Six dyes.
Related additives
Common questions
Is E133 banned in the UK?
No. E133 is approved for use in the UK under the assimilated EU Regulation (EC) No 1333/2008 and appears on the UK FSA's list of authorised additives. It is not subject to the Southampton hyperactivity warning label that applies to E102, E104, E110, E122, E124 and E129.
Why is the US trying to phase out Brilliant Blue FCF?
In April 2025 the US HHS and FDA announced a voluntary initiative with food manufacturers to remove FD&C Blue No. 1 (the US name for Brilliant Blue FCF) and five other petroleum-based certified dyes from the food supply by end of 2027. The announcement cited a broader policy shift away from petroleum-derived synthetic colours. It is a voluntary agreement with industry, not a formal regulatory ban, and it does not apply in the UK or EU.
What foods contain E133?
Blue and blue-raspberry flavoured sweets, ice lollies, slush drinks and sports drinks are the most common sources. It also appears in some cake icings, blue ice cream, packet soups, flavoured jellies, and tinned mushy peas (combined with a yellow dye to make green). On UK labels it will be listed as Brilliant Blue FCF or E133.
Is E133 vegan?
The dye itself is synthetic and does not contain animal-derived ingredients. However, some formulations use an aluminium lake version of the dye. Historically, lab-animal testing was conducted to establish safety data, which some vegans consider relevant. The dye is not flagged as non-vegan by UK food labelling rules.
Sources
- UK FSA Regulated Products Database: E133 Brilliant Blue FCF
- EFSA Panel on Food Additives (ANS): Scientific Opinion on the re-evaluation of Brilliant Blue FCF (E 133) as a food additive, EFSA Journal 2010
- JECFA: Brilliant Blue FCF monograph and evaluation summary, WHO Food Additives database
- Lau K et al., Synergistic interactions between commonly used food additives in a developmental neurotoxicity test, Toxicological Sciences, 2006
- Tanaka T et al., Reproductive and neurobehavioral effects of Brilliant Blue FCF in mice, Birth Defects Research Part B, 2012
- Rambler et al., A Review of the Association of Blue Food Coloring With Attention Deficit Hyperactivity Disorder Symptoms in Children, Cureus, 2022
- Amchova P et al., Food Safety and Health Concerns of Synthetic Food Colors: An Update, Toxics, 2024
- Olas B et al., The Effects of Natural and Synthetic Blue Dyes on Human Health: A Review of Current Knowledge and Therapeutic Perspectives, Advances in Nutrition, 2021
- Modulation of immune functions, inflammatory response, and cytokine production following long-term oral exposure to three food additives: thiabendazole, monosodium glutamate, and brilliant blue in rats, PubMed PMID 34182247
- US HHS/FDA press announcement: HHS, FDA to Phase Out Petroleum-Based Synthetic Dyes in Nation's Food Supply
- Wikipedia: Brilliant blue FCF
Aaron Keen is the founder of NutraSafe. He researches and writes every additive entry himself, from the primary sources. About the research →
This is a guide, not medical advice. If an additive affects you, speak to your GP or a dietitian.
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