Brown FK
A synthetic brown dye made from six coal-tar-derived azo chemicals, developed specifically to colour kippers. Removed from EU and UK approved lists after regulators could not confirm it was safe.
Both EU regulators and the global UN food safety committee reviewed Brown FK and could not establish any safe intake level, citing gaps in cancer and toxicity data. Azo dyes in this class can break down in the gut to aromatic amines, some of which have carcinogenic properties.
What is it?
A brown food colour made from a mixture of six synthetic azo dyes combined with sodium chloride and sodium sulphate. Produced from coal-tar chemistry. The name FK stands for 'For Kippers', the only food it was ever approved to colour in the UK. It is water-soluble and heat-stable, making it suitable for dyeing smoked fish that would otherwise lose colour during curing and cooking.
What does it do?
Deposits a persistent reddish-brown colour into the surface of smoked herring, masking the paler appearance that results from reduced smoking time. The dye resists leaching during cooking because it binds to proteins in the fish flesh. It has no flavour or preservative function.
Where you will see it
Historically used only in kippers (smoked herrings) in the UK, where it was applied by fish curers to produce the deep reddish-brown colour associated with a traditionally smoked kipper. It was also used in some cured mackerel and cooked meats. It is no longer approved anywhere in the EU or UK. Products sold today that have a kipper colour use annatto (E160b), a natural pigment derived from achiote seeds. On labels it would appear as 'Brown FK' or 'E154'.
What the science says
Regulators could not confirm it was safe
When the European Food Safety Authority re-evaluated Brown FK in 2010, it concluded that the available toxicity data were too incomplete to make a safety determination. A key long-term rat study showed treatment-related changes at the highest dose, but the lower dose groups had not been examined histologically, making it impossible to identify a level at which no harmful effects occurred. On that basis EFSA recommended the additive not be included in the approved list.
EFSA concluded it could not determine a safe intake level for Brown FK due to deficiencies in the toxicity database, including incomplete histopathological examination of animals in a long-term carcinogenicity study.
JECFA assigned a temporary ADI of 0-0.075 mg/kg body weight in 1985 (29th meeting, WHO TRS 733), then withdrew it in 1986 (30th meeting, WHO TRS 751) when it concluded that no ADI could be allocated due to inadequate toxicological data.
Azo dye breakdown and aromatic amine risk
Brown FK is a mixture of azo dyes, meaning its molecules contain nitrogen-nitrogen double bonds that gut bacteria and liver enzymes can cleave. This reduction process releases aromatic amines, a chemical class that includes known human carcinogens. Whether the specific amines released by Brown FK are harmful at food exposure levels was one of the unresolved questions flagged during EFSA's re-evaluation.
Azo dyes can be metabolised in humans through reductive cleavage to aromatic amines; some of these metabolites have mutagenic or carcinogenic properties depending on their structure.
Genotoxicity testing of Brown FK and related azo dyes in bacterial systems found activity linked to amino substituents and azo-reduction products; results were not uniformly negative across test conditions.
Asthma and hypersensitivity
Like other azo dyes, Brown FK has been identified as a histamine liberator, meaning it can trigger the release of histamine in sensitive individuals. This can worsen asthma symptoms and may cause hives, eczema, or breathing difficulties in people with salicylate sensitivity. The evidence for Brown FK specifically is limited because it was rarely used and data were not gathered at scale.
Brown FK, as an azo dye, is classed as a histamine liberator that may exacerbate asthma symptoms in susceptible individuals.
EFSA noted that no well-documented cases of intolerance reactions after oral exposure to Brown FK had been formally reported in the scientific literature, partly because use of the dye was so restricted.
Hyperactivity and benzoate combination
When azo dyes are consumed alongside benzoate preservatives, there is an association with increased hyperactive behaviour in children. The Southampton study demonstrated this for a mixture of six azo dyes plus sodium benzoate. Brown FK was not among the six colours tested in that specific trial, but it belongs to the same chemical class and was often used alongside benzoates in cured fish products.
A randomised controlled trial found that a mixture of six azo food dyes with sodium benzoate significantly increased hyperactivity in children aged 3 and 8-9 years compared to placebo.
Where it stands with the regulators
Who should be careful
Anyone with asthma, salicylate sensitivity, or a known azo dye intolerance should be aware of this additive. Because it is no longer approved in the UK or EU, it should not appear in products sold here. If you are buying imported smoked fish from a country where E154 may still be permitted, check the label for 'Brown FK' or 'E154'.
The honest read
The honest picture is that regulatory science never cleared this dye. Neither JECFA in 1986 nor EFSA in 2010 could establish a dose at which Brown FK was confirmed to cause no harm, because the long-term animal studies that would have answered that question were not adequately done. That is not the same as evidence that it causes cancer in people, but it is why regulators removed it from the approved list rather than setting a limit. It was also a dye used to make pale, less-smoked kippers look more traditionally smoked, a cosmetic function with no benefit to the consumer. It no longer appears in UK or EU food products.
Related additives
Common questions
Is E154 banned in the UK?
E154 is not permitted in UK food products. It was excluded from the EU's Union list of approved food additives by Commission Regulation 1129/2011, which noted that regulators could not confirm its safety due to gaps in toxicity data. That exclusion forms part of UK law. The UK FSA's current list of approved additives does not include E154. It was previously permitted in kippers at 20mg/kg under the 1995 Colours in Food Regulations, but that approval lapsed when EU-wide rules took precedence.
Why was Brown FK removed from the approved list?
The European Food Safety Authority re-evaluated it in 2010 and concluded that the available toxicity studies had significant gaps. A key long-term rat study showed effects at high doses but lower dose groups had not been properly examined, so no safe intake level could be established. JECFA had already reached the same conclusion in 1986, withdrawing its provisional acceptable daily intake. Regulators decided not to include it on the approved list rather than permit it with unresolved safety questions.
What foods contain E154?
It was historically used only in kippers in the UK, and to a lesser extent in some cured mackerel and cooked meats. It is no longer approved in the UK or EU, so it should not appear in any products sold here. Modern kippers that have an orange-brown colour use annatto (E160b), a natural pigment, instead.
Is E154 vegan?
Brown FK is a synthetic coal-tar-derived dye with no animal ingredients. It would be considered vegan in terms of its composition. However, it is not permitted in UK or EU food products, so this question is largely academic for anyone buying food in these markets.
Sources
- EFSA Scientific Opinion on the re-evaluation of Brown FK (E 154) as a food additive
- Commission Regulation (EU) No 1129/2011 establishing the Union list of food additives
- UK FSA: Approved additives and E numbers
- JECFA evaluation of Brown FK (29th meeting 1985, TRS 733; 30th meeting 1986, TRS 751)
- The Colours in Food Regulations 1995 (SI 1995/3124)
- Brown FK, Wikipedia
- McCann et al. Food additives and hyperactive behaviour in 3-year-old and 8/9-year-old children in the community, The Lancet
- Mutagenicity and carcinogenicity of aromatic amines metabolically produced from azo dyes, Journal of Environmental Science and Health Part C
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