Quinoline Yellow
A synthetic greenish-yellow dye added to drinks, sweets, and sauces. One of the Southampton Six colours that carry a mandatory children's hyperactivity warning in the UK.
Part of the Southampton Six, a group of dyes linked to increased hyperactivity in children in an FSA-funded randomised trial. UK law requires any food containing it to carry the warning 'may have an adverse effect on activity and attention in children'. Lab studies have also found it activates a receptor linked to disruption of oestrogen signalling, though regulators have not yet acted on those findings.
What is it?
Quinoline Yellow (E104) is a synthetic dye made by sulfonating 2-(2-quinolyl)-1,3-indandione, a compound produced from quinaldine and phthalic anhydride. The food-grade form is the water-soluble sodium salt, sold as Quinoline Yellow WS. It is not approved for food use in the United States or Australia. In the US it is permitted only in externally applied cosmetics and drugs under the name D&C Yellow No. 10.
What does it do?
It imparts a greenish-yellow hue to food and drink. It is relatively light-stable and does not react with other common food ingredients, making it useful for colouring products where a consistent warm yellow is needed over shelf-life.
Where you will see it
Found in smoked fish products such as haddock and smoked cod, flavoured soft drinks, confectionery including boiled sweets and chewing gum, mustard, sauces, desserts, fish roe, aromatised wines, and some food supplements. Many major UK manufacturers removed it voluntarily after the 2007 Southampton study, but it can still appear in some imported sweets, drinks, and bakery items. On a UK label it appears as 'Quinoline Yellow' or 'E104', always accompanied by the children's hyperactivity warning.
What the science says
Children's behaviour and the Southampton study
An FSA-funded randomised double-blind placebo-controlled trial published in The Lancet tested mixtures of six artificial colours, including Quinoline Yellow, combined with sodium benzoate, in children aged 3 and 8-9. Children who consumed the colour-and-preservative mixture showed significantly higher hyperactivity scores than those given plain fruit juice. The study did not test E104 alone, so whether Quinoline Yellow specifically drives the effect, or whether it requires the full mixture, cannot be determined from this trial.
A randomised double-blind placebo-controlled trial found that a mixture of six artificial food colours including E104 and sodium benzoate significantly increased hyperactive behaviour in children aged 3 and 8-9 from the general population.
Following the McCann trial, EU legislation made it mandatory to label any food or soft drink containing one of the six colours with 'may have an adverse effect on activity and attention in children'.
EFSA re-evaluation and lowered acceptable daily intake
In 2009 the European Food Safety Authority re-evaluated Quinoline Yellow and cut its acceptable daily intake 20-fold, from 10 mg/kg body weight per day to 0.5 mg/kg. The reduction was driven by a previously unconsidered animal study on reproductive and developmental effects in rats and by hypersensitivity reports. A refined EFSA exposure assessment in 2015 found that high-level consumers, particularly young children eating confectionery and flavoured drinks, could approach or exceed the lowered ADI.
EFSA's ANS Panel lowered the ADI for Quinoline Yellow from 10 mg/kg to 0.5 mg/kg body weight per day, applying a 100-fold uncertainty factor to the NOAEL from a chronic rat study with a reproductive toxicity phase.
A refined EFSA exposure assessment found that the highest dietary intake of E104 is in toddlers and children, estimated at up to 0.40 mg/kg body weight per day, approaching the 0.5 mg/kg ADI under high-consumption scenarios.
Hypersensitivity reactions
Case reports and the 2009 EFSA review note that some individuals experience urticaria (hives), rhinitis, and bronchial asthma after consuming Quinoline Yellow. People with aspirin sensitivity or known reactions to other synthetic dyes appear to be at higher risk. EFSA noted that the available data were insufficient to determine whether Quinoline Yellow alone triggers these reactions or whether a mixture is required.
Reports linked Quinoline Yellow consumption to urticaria, rhinitis, and asthma, most often in individuals sensitive to aspirin or other synthetic dyes, frequently in the context of multi-colour mixtures.
Genotoxicity: mixed picture from lab studies
Long-term carcinogenicity studies in animals have been negative, and EFSA's 2009 review did not classify Quinoline Yellow as a genotoxin. However, a 2004 in vitro study using human lymphocytes found evidence of DNA damage using the Comet assay and micronucleus test. A separate 2015 study in human liver cells found DNA strand breakage and chromosome damage at low concentrations. These in vitro results have not translated to findings in standard animal guideline studies, and EFSA's position remains that the dye does not raise genotoxicity concerns at food-use levels.
Testing in human lymphocytes and plant root-tip cells found evidence of DNA damage in the Comet assay and micronucleus test, indicating genotoxic potential in vitro.
Low concentrations of Quinoline Yellow (0.5-20 micrograms/mL) were genotoxic in human HepG2 liver cells using both the Comet assay and cytokinesis-block micronucleus cytome assay, with genotoxic metabolites identified after simulated liver metabolism.
EFSA's 2009 re-evaluation found Quinoline Yellow negative in standard in vitro genotoxicity tests and long-term carcinogenicity studies, and did not classify it as a genotoxin at food-use levels.
Endocrine disruption signals in laboratory research
A 2020 study by researchers at the German Federal Institute for Risk Assessment found that Quinoline Yellow is the most potent activator of the aryl hydrocarbon receptor (AhR) among a group of yellow dyes tested, and that AhR activation in turn suppressed oestrogen receptor signalling. The researchers described this as raising potential toxicological concern and called for systematic screening. This research used cell lines and has not been evaluated by food safety regulators.
Quinoline Yellow was identified as the most potent agonist of the aryl hydrocarbon receptor among related yellow dyes, and was shown to inhibit oestrogen receptor signalling in an AhR-dependent manner in MCF7 cells, raising potential endocrine disruption concern.
Developmental toxicity in zebrafish embryos
A 2025 study exposed zebrafish embryos to Quinoline Yellow and found heart oedema, yolk sac necrosis, blood stasis, and reduced eye size at concentrations of 0.5 mg/mL and above, with a lethal concentration of 0.64 mg/mL. The researchers called for further evaluation of developmental safety. These concentrations are far higher than any dietary exposure from food, so direct translation to human health risk is uncertain.
Zebrafish embryos exposed to Quinoline Yellow at 0.5 mg/mL and above showed pericardial oedema, yolk sac necrosis, blood stasis, and microphthalmia, with a lethal concentration of 0.64 mg/mL; researchers called for re-evaluation of current safety thresholds.
Where it stands with the regulators
Who should be careful
Parents who want to limit the Southampton Six colours for their children should check labels for 'Quinoline Yellow' or 'E104', which must always appear with the warning 'may have an adverse effect on activity and attention in children'. Anyone with aspirin sensitivity or known reactions to synthetic dyes such as tartrazine (E102) should watch for it, as cross-reactivity has been reported.
The honest read
Quinoline Yellow sits at the centre of a live regulatory debate. Its ADI was cut 20-fold in 2009, and the mandatory children's warning was introduced because the science was strong enough to act on, even though the Southampton study tested a mixture of six colours and could not pin the effect on E104 alone. Exposure modelling suggests that children who eat a lot of coloured confectionery and soft drinks can approach the lowered ADI. Lab studies have raised additional questions about DNA damage and interference with oestrogen receptor signalling, though these findings use concentrations well above dietary exposure and have not been evaluated by food safety regulators in a formal re-assessment. EFSA has not classified it as a carcinogen or genotoxin. The picture is one of a colour that regulators have progressively restricted as evidence has accumulated, with live questions that have not yet been fully resolved.
Related additives
Common questions
Is E104 banned in the UK?
No. Quinoline Yellow is still a permitted food additive in the UK under assimilated EU Regulation 1333/2008. However, the FSA encouraged manufacturers to remove it voluntarily after the 2007 Southampton study, and any food or soft drink that still contains it must carry the warning 'may have an adverse effect on activity and attention in children'. It is not authorised for food use in the United States or Australia.
Why does E104 carry a children's warning?
An FSA-funded randomised trial published in The Lancet in 2007 found that a mixture of six artificial colours including E104, combined with the preservative sodium benzoate, significantly increased hyperactive behaviour in children aged 3 and 8-9. EU law from 2010 made it mandatory to label any food containing one of these six colours with 'may have an adverse effect on activity and attention in children'. The study tested the colours as a group, not E104 in isolation, so the individual contribution of Quinoline Yellow cannot be separated.
What foods contain E104?
It can appear in flavoured soft drinks, boiled sweets, chewing gum, candied fruit, confectionery coatings, smoked fish products such as haddock and smoked cod, mustard, sauces, desserts, fish roe, aromatised wines, and some food supplements. Many major UK brands removed it after 2007. Look for 'Quinoline Yellow' or 'E104' on the ingredients list.
Is E104 vegan?
Quinoline Yellow is a fully synthetic dye with no animal-derived raw materials in the dye itself, so it is generally considered vegan in origin. However, some commercial preparations use gelatin as a carrier, which is animal-derived. If vegan status matters, check with the specific manufacturer or look for a certified vegan product mark.
Sources
- McCann et al., 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, The Lancet, 2007
- EFSA ANS Panel, Scientific Opinion on the re-evaluation of Quinoline Yellow (E 104) as a food additive, EFSA Journal, 2009
- EFSA, Refined exposure assessment for Quinoline Yellow (E 104), EFSA Journal, 2015
- UK Food Standards Agency, Approved additives and E numbers
- UK Food Standards Agency, Food additives (hyperactivity warning colours)
- UK FSA Regulated Products, E104 Quinoline Yellow authorisation record
- Commission Regulation (EU) No 232/2012 amending Annex II to Regulation (EC) No 1333/2008 as regards conditions of use for Quinoline Yellow (E 104), Sunset Yellow (E 110) and Ponceau 4R (E 124)
- Macioszek and Kononowicz, The evaluation of the genotoxicity of two commonly used food colors: Quinoline Yellow (E 104) and Brilliant Black BN (E 151), Cell Mol Biol Lett, 2004
- Chequer et al., The cosmetic dye quinoline yellow causes DNA damage in vitro, Mutation Research - Genetic Toxicology and Environmental Mutagenesis, 2015
- Tarnow et al., Characterization of Quinoline Yellow Dyes As Transient Aryl Hydrocarbon Receptor Agonists, Chemical Research in Toxicology, 2020
- Majdan et al., Assessment of embryotoxic effects of Quinoline Yellow using attention-based convolutional neural network and machine learning in zebrafish model, Frontiers in Pharmacology, 2025
- University of Southampton, Major study indicates a link between hyperactivity in children and certain food additives, 2007
- Norwegian Food Safety Authority (Mattilsynet), Food additives, enzymes and flavourings
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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