also: Chocolate Brown HT · Food Brown 3 · CI 20285
A synthetic brown azo dye used to mimic the colour of cocoa or caramel in chocolate-flavoured baked goods and confectionery.
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As an azo dye, Brown HT is broken down by gut bacteria into aromatic amines, some of which have shown carcinogenic potential in related compounds.
2
of the 43,325 UK supermarket foods we checked declare E155 in their ingredients
That is under 0.1%, counted by its code or its name.
Counted by NutraSafe from UK supermarket ingredient lists, September 2026. How we counted
Why it’s worth knowing. As an azo dye, Brown HT is broken down by gut bacteria into aromatic amines, some of which have shown carcinogenic potential in related compounds. It can trigger asthma attacks and hives in people with aspirin intolerance or salicylate sensitivity. EFSA halved its acceptable daily intake in 2010 after animal studies found adverse effects at lower doses than previously used to set the limit.
Brown HT (also called Chocolate Brown HT, Food Brown 3, CI 20285) is a synthetic diazo dye made from coal tar-derived aromatic compounds. Its molecular formula is C27H18N4Na2O9S2. It carries two azo groups (-N=N-) linking aromatic rings, giving it a deep brown colour that is highly soluble in water.
It colours food brown by absorbing light in the blue-green spectrum and reflecting brown wavelengths. In food manufacturing it substitutes for cocoa, caramel, or other natural brown pigments. It is stable to heat, light, and the pH ranges typical in baked goods.
Primarily used in chocolate-flavoured cakes, biscuits, pastries, and dessert mixes. Also appears in some confectionery, flavoured dairy products, chocolate drinks, ice cream, jams, and processed fish products. On a label it appears as 'Brown HT' or 'E155'.
In 2010, EFSA completed a full re-evaluation of Brown HT and cut the acceptable daily intake from 3 mg/kg body weight per day (the level set by the EU's Scientific Committee on Food) to 1.5 mg/kg per day. The reduction was driven by long-term animal studies showing adverse effects, including slightly reduced weight gain, at doses lower than those previously used to set the limit. EFSA also noted data gaps and requested further toxicological studies.
EFSA reduced the ADI for Brown HT from 3 mg/kg bw/day to 1.5 mg/kg bw/day after a long-term carcinogenicity and toxicity study in mice showed adverse effects at lower doses than previously evaluated.
JECFA independently established an ADI of 0 to 1.5 mg/kg bw/day for Brown HT, consistent with EFSA's 2010 conclusion.
Gut bacteria carry enzymes called azoreductases that cleave the azo bonds in dyes like Brown HT, releasing aromatic amine breakdown products. Some of these metabolites have mutagenic or carcinogenic properties, even when the parent dye itself is not classified as carcinogenic. Researchers have noted that current regulatory safety assessments may not fully account for the toxicity of these in-gut metabolites.
Human intestinal microbiota can reduce azo dyes to aromatic amines; some of these metabolites, including o-toluidine (IARC Group 1) and benzidine, have been shown to be carcinogenic, even when the parent azo dye is not classified as such.
Further studies on the in vivo reduction of azo food dyes by human gut bacteria and the potential to produce genotoxic aromatic compounds are needed; current regulatory assessments may be incomplete.
Like other azo dyes, Brown HT can provoke pseudo-allergic reactions in people who are sensitive to aspirin or non-steroidal anti-inflammatory drugs. Reactions range from hives and skin rashes to worsening asthma. The dye also acts as a histamine liberator, which can intensify asthma symptoms. Evidence for these reactions is better established for azo dyes as a class than for Brown HT in isolation.
Brown HT may intensify asthma symptoms and trigger adverse reactions in people sensitive to aspirin or salicylates through histamine liberation and pseudo-allergic mechanisms.
Azo dyes as a class are associated with bronchoconstriction and urticaria in aspirin-sensitive individuals; cross-reactivity among structurally similar azo dyes is documented.
The 2007 McCann et al. Southampton study prompted EFSA to review azo dyes for links to hyperactivity in children. The Southampton Six colours (E102, E104, E110, E122, E124, E129) were found to have the strongest association. EFSA's 2010 review of Brown HT did not result in its inclusion in the EU's mandatory hyperactivity warning list, and Brown HT was not directly tested in the Southampton study. EFSA noted, however, that as a precautionary measure, limiting children's intake of azo dyes broadly was reasonable.
Following the McCann et al. 2007 Southampton study, EFSA reviewed Brown HT but did not add it to Annex V of Regulation 1333/2008, which requires the mandatory 'may have an adverse effect on activity and attention in children' warning label. That list covers only E102, E104, E110, E122, E124, and E129.
McCann et al. found that a mixture of six synthetic food colours and sodium benzoate increased hyperactivity in 3-year-old and 8 to 9-year-old children; Brown HT was not one of the colours tested.
Brown HT is not approved in the United States (where it was never authorised for food, drug or cosmetic use), Australia, and a number of European countries including Germany, France, Belgium, Austria, Denmark, Norway, Sweden, and Switzerland. It remains permitted in the UK and EU under specific conditions of use. This widespread prohibition by some regulators reflects differing risk tolerances and data-sufficiency standards, not a settled scientific consensus that it is unproblematic.
Brown HT has never been authorised for use in food, drugs or cosmetics in the United States.
E155 is authorised in England, Scotland and Wales under assimilated Regulation (EU) No 1333/2008 and classified as a Group III food colour with a combined maximum limit alongside other approved colours.
People with asthma, aspirin intolerance, or salicylate sensitivity may react to Brown HT. Those with known sensitivities to other azo dyes should also treat it with caution, as cross-reactions are possible. Look for 'Brown HT' or 'E155' on the ingredients list, most commonly on chocolate-flavoured baked goods, biscuits, and dessert products.
Brown HT sits in an uncomfortable middle ground: permitted in the UK and EU, but banned by many comparable food regulators including in the USA and across much of northern Europe. EFSA's 2010 re-evaluation reduced the acceptable daily intake after animal studies found harm at lower doses than previously recognised, and researchers have flagged that standard safety assessments do not fully account for the aromatic amine compounds produced when gut bacteria break down azo dyes. The hyperactivity evidence does not directly implicate Brown HT, but the broader azo dye class drew regulatory attention from the Southampton study. The science on azo dye gut metabolism and long-term effects is still developing.
No. E155 is approved for use in the UK under assimilated EU Regulation 1333/2008 and appears on the FSA's approved additives list. However, it is banned in several other countries including the USA, Australia, Germany, France, Belgium, Austria, Denmark, Norway, Sweden, Switzerland, and Russia.
No. The mandatory 'may have an adverse effect on activity and attention in children' warning under EU Regulation 1333/2008 Annex V applies only to six colours: E102, E104, E110, E122, E124, and E129. E155 is not in that group and does not legally require that warning. Brown HT was not one of the dyes tested in the original Southampton study.
E155 is used mainly in chocolate-flavoured cakes, biscuits, pastries, and dessert mixes. It also appears in some chocolate drinks, flavoured dairy products, confectionery, ice cream, and processed foods where a brown colour is wanted without cocoa or caramel. Check for 'Brown HT' or 'E155' on the ingredients list.
Yes. Brown HT is a fully synthetic dye derived from coal tar chemistry. It contains no animal-derived ingredients and is acceptable for vegans and vegetarians.
Last reviewed: 20 June 2026
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