Sunset Yellow
A synthetic orange azo dye from petroleum, added to food and drinks to give a yellow-to-orange colour.
One of the Southampton Six colours linked to increased hyperactivity in children in a 2007 UK government-funded trial. All products containing it must carry the label warning 'may have an adverse effect on activity and attention in children'. Some people with aspirin intolerance or chronic urticaria report skin reactions.
What is it?
Sunset Yellow FCF (also called Orange Yellow S) is a synthetic azo dye made from petroleum-derived chemicals. Its chemical structure contains two nitrogen atoms linked by a double bond, which is the defining feature of the azo family of dyes. It produces a stable orange-yellow colour and is water-soluble.
What does it do?
The dye absorbs light in the blue-violet part of the spectrum and transmits orange-yellow wavelengths, giving food its colour. It does not contribute flavour, texture, or nutritional value. It is stable to heat and to most food processing conditions.
Where you will see it
Orange and lemon squashes, flavoured carbonated drinks (including Irn-Bru), sweets and confectionery, fish roe and smoked salmon substitutes, mustard, savoury sauces and pickles, marzipan, desserts, and some food supplements. On an ingredients label it appears as 'Sunset Yellow FCF', 'Orange Yellow S', or 'E110'.
What the science says
Hyperactivity and attention in children
A 2007 UK government-funded double-blind crossover trial found that children aged 3 and 8-9 who consumed drinks containing a mixture of six artificial colours including E110 and sodium benzoate showed measurably increased hyperactivity compared to when they drank the placebo. EFSA reviewed the same study and concluded the evidence showed a small effect in some children, but was not consistent across the two age groups and the two mixtures tested. Meta-analyses of multiple such studies find modest effect sizes from artificial food colour elimination, with parent ratings showing larger effects than teacher or observer ratings, and the overall effect too small to be recommended as a standalone ADHD treatment.
Children aged 3 and 8-9 who consumed a mixture of artificial food colours including E110 plus sodium benzoate showed significantly increased hyperactivity compared to placebo in a double-blind, placebo-controlled crossover trial.
EFSA concluded the Southampton study provided limited evidence of a small effect on activity and attention in some children, but the results were not consistent across age groups or the two colour mixtures tested.
A systematic review of meta-analyses of double-blind placebo-controlled trials found artificial food colour elimination produced effect sizes of 0.21-0.44 on parent ratings of hyperactivity, but 0.08-0.11 on teacher and observer ratings, concluding the effects were too small to recommend as a general ADHD treatment.
Mandatory UK and EU warning label
Under Article 24 of EU Regulation 1333/2008, which became compulsory from 20 July 2010 and is retained in UK law post-Brexit, any food or drink containing E110 must carry the warning 'may have an adverse effect on activity and attention in children'. This is a legal labelling requirement, not a voluntary advisory. The FSA recommended voluntary withdrawal by manufacturers in 2008, and many UK brands reformulated to remove it, though it remains a permitted additive.
Any food or drink containing E110 must display the warning 'may have an adverse effect on activity and attention in children' under Article 24 of EU Regulation 1333/2008, mandatory from July 2010 and retained in UK assimilated law.
The FSA recommended in 2008 that UK manufacturers voluntarily phase out the use of the six colours including E110 by the end of 2009, following its review of the Southampton study.
Skin reactions and aspirin-sensitive individuals
Because E110 is an azo dye, it can trigger pseudo-allergic reactions (not true IgE allergy) in people with aspirin intolerance, salicylate sensitivity, or chronic urticaria. EFSA's 2010 opinion on azo dyes noted that intolerance reactions to E110 have been reported, including urticaria and angioedema, though the frequency is low. A placebo-controlled oral challenge study in chronic urticaria patients found only 5.1% of those tested positive to a mixture of six azo dyes, indicating that confirmed hypersensitivity is much less common than patient self-report.
EFSA reviewed evidence on azo dyes and concluded that intolerance reactions to Sunset Yellow FCF have been reported in sensitive individuals, including urticaria and angioedema, but that consumption at permitted levels is unlikely to cause serious hypersensitivity reactions in the general population.
In a placebo-controlled oral challenge study of 110 chronic urticaria patients, only 2 of 39 patients (5.1%) tested positive to a capsule containing a mixture of six azo dyes including E110, suggesting confirmed azo-dye hypersensitivity is much less common than patient-reported rates.
Testicular effects in rat studies and ADI history
In 2009, EFSA temporarily reduced the acceptable daily intake (ADI) for E110 from 2.5 to 1 mg/kg body weight per day after rat studies by Mathur et al. reported effects on testis weight and sperm at high doses. However, the test material in those studies was of unspecified purity and sourced from a local market. Subsequent reviews found the testicular effects were not consistently reproduced in longer-duration rat studies using certified high-purity material. In 2014, EFSA lifted the temporary restriction and set the current ADI at 4 mg/kg body weight per day, based on a long-term rat feeding study with a NOAEL of 375 mg/kg bw/day.
EFSA set a temporary reduced ADI of 1 mg/kg bw/day for E110 in 2009, applying an extra uncertainty factor of 2.5, after rat studies by Mathur et al. reported effects on testes at 250 mg/kg bw/day and above. The test compound's purity was unconfirmed.
After reviewing new data including studies with certified-purity material, EFSA concluded there was no genotoxicity concern and no consistent testicular finding, and restored the ADI to 4 mg/kg bw/day based on a NOAEL of 375 mg/kg bw/day from a long-term rat feeding study.
Laboratory findings at high doses
Animal studies at doses well above typical human dietary exposure have found markers of oxidative stress and changes to liver and kidney tissue in rats given E110 daily. One study also reported slight genotoxic signals in rat cells. These are laboratory findings in animals given the dye in isolation at high concentrations; they do not directly predict effects from food consumption at UK-permitted levels.
Male rats given Sunset Yellow at 2.5 mg/kg bw/day for four weeks showed elevated liver enzymes, increased kidney markers, and signs of oxidative stress including higher MDA levels and reduced antioxidant activity, alongside histological changes to liver and kidney tissue.
An in vivo micronucleus test in mice found no genotoxic activity for Sunset Yellow FCF at doses up to 2000 mg/kg bw, supporting EFSA's conclusion of no genotoxicity concern.
Sunset Yellow and Orange II were tested for genotoxicity by gavaging rodents and checking bile, urine, faecal and bone marrow extracts using the Ames test. Standard extracts were negative; however, faecal extracts from Sunset Yellow-treated animals showed increased revertants with one Salmonella strain when exogenous metabolic activation was applied, suggesting gut bacteria may convert E110 into weakly mutagenic metabolites.
Where it stands with the regulators
Who should be careful
Children whose parents or caregivers want to reduce exposure to the Southampton Six colours, given the mandatory hyperactivity warning. People with aspirin intolerance, salicylate sensitivity, or a history of chronic urticaria or angioedema, as azo dyes can trigger pseudo-allergic reactions in these groups. Look for 'Sunset Yellow FCF', 'Orange Yellow S', or 'E110' on the ingredients list. The mandatory warning 'may have an adverse effect on activity and attention in children' must appear on any product containing it.
The honest read
The hyperactivity signal from the Southampton Six is the most consistently discussed concern around E110. The 2007 Lancet trial was government-funded, double-blind, and placebo-controlled, which is why it drove regulatory action. But the effect it found is modest, was not uniform across the two age groups or mixtures tested, and subsequent meta-analyses find effect sizes too small to warrant artificial colour elimination as a primary ADHD intervention. What is settled: the UK mandatory warning label is law, and the FSA recommended manufacturers remove it. What is not settled: whether the hyperactivity effect is meaningful for individual children in ordinary diets, and whether any single colour in the mixture drives it. The temporary ADI reduction in 2009 over rat testicular findings was lifted in 2014 when higher-quality studies did not replicate the effect. Lab studies in animals at high doses continue to find oxidative stress markers; human relevance at permitted dietary exposure levels has not been established. The picture is a low-level, real but modest signal in children, an acknowledged intolerance risk in aspirin-sensitive individuals, and a legal warning requirement that is not in dispute.
Related additives
Common questions
Is E110 banned in the UK?
No. E110 is an approved food additive in the UK under the assimilated EU Regulation 1333/2008. It is not banned. However, from July 2010 any product containing it must carry a mandatory warning: 'may have an adverse effect on activity and attention in children'. The UK FSA recommended in 2008 that manufacturers voluntarily remove it, and many UK brands did so, but it remains lawfully permitted.
Why does E110 have a warning label?
The warning follows a 2007 University of Southampton study, funded by the FSA, which found that children who consumed a mixture of six artificial colours including E110 and the preservative sodium benzoate showed increased hyperactivity compared to a placebo. The EU made the warning label mandatory from 20 July 2010 under Article 24 of Regulation 1333/2008. The label applies to any product containing any of the six colours, not just E110 alone.
What foods contain E110?
E110 appears in flavoured carbonated drinks (including Irn-Bru), orange and lemon squashes, sweets and confectionery, mustard, savoury sauces and pickles, smoked salmon substitutes and fish roe, some desserts and marzipan. Many mainstream UK food and drink brands voluntarily reformulated to remove it after 2008, but it is still found in some products, particularly imported confectionery and certain soft drinks. Check the ingredients list for 'Sunset Yellow FCF', 'Orange Yellow S', or 'E110'.
Is E110 vegan?
E110 is a petroleum-derived synthetic dye and contains no animal ingredients, making it acceptable to most vegans on an ingredient basis. Some vegans avoid it on ethical grounds because artificial food dyes are subject to ongoing animal testing as part of regulatory safety monitoring.
Sources
- UK FSA: Approved additives and E numbers - E110 Sunset Yellow FCF
- UK FSA Regulated Products Register: E110
- UK FSA: Food additives (Southampton Six and warning labels)
- McCann et al. - Food additives and hyperactive behaviour in 3-year-old and 8/9-year-old children: a randomised, double-blinded, placebo-controlled trial. The Lancet.
- EFSA AFC Panel - Assessment of McCann et al. 2007 Southampton study. EFSA Journal.
- EFSA ANS Panel - Scientific Opinion on re-evaluation of Sunset Yellow FCF (E110) as a food additive. EFSA Journal 7(11):1330.
- EFSA ANS Panel - Reconsideration of the temporary ADI and refined exposure assessment for Sunset Yellow FCF (E110). EFSA Journal 12(7):3765.
- EFSA ANS Panel - Scientific Opinion on appropriateness of food azo-colours for inclusion in allergen labelling list. EFSA Journal 8(10):1778.
- Commission Regulation (EU) No 232/2012 amending Annex II to Regulation (EC) No 1333/2008 regarding conditions of use for E110
- Nigg et al. - Diet and ADHD, Reviewing the Evidence: A Systematic Review of Meta-Analyses of Double-Blind Placebo-Controlled Trials. PLOS ONE.
- Ahmed et al. - Sunset Yellow and Allura Red modulate Bcl2 and COX2 expression levels and confer oxidative stress-mediated renal and hepatic toxicity in male rats. Toxicology Reports.
- Hypersensitivity of azo dyes in urticaria patients based on a single-blind, placebo-controlled oral challenge. PMC9704453.
- Akhaltseva et al. - Evaluation of the genotoxicity of the food dye Sunset Yellow FCF in a micronucleus test in vivo. Hygiene and Sanitation.
- Wever et al. - Testing of sunset yellow and orange II for genotoxicity in different laboratory animal species. Environmental and Molecular Mutagenesis.
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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