also: Acid Yellow 17 · C.I. 18965 · Food Yellow 5
A synthetic yellow azo dye not permitted in UK or EU food, withdrawn after regulators could not establish any acceptable daily intake.
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As an azo dye, Yellow 2G can trigger urticaria, asthma attacks and other hypersensitivity reactions, particularly in people who are sensitive to aspirin.
Why it’s worth knowing. As an azo dye, Yellow 2G can trigger urticaria, asthma attacks and other hypersensitivity reactions, particularly in people who are sensitive to aspirin. Regulators withdrew it because safety data were insufficient to set any acceptable intake level.
Yellow 2G is a synthetic azo dye made from aromatic precursors (historically derived from coal tar). Its chemical name is disodium 2,5-dichloro-4-[3-methyl-5-oxo-4-(4-sulfonatophenyl)diazenyl-4H-pyrazol-1-yl]benzenesulfonate (CAS 6359-98-4). It is water-soluble and produces a yellow to greenish-yellow colour. Also known as Acid Yellow 17 and CI Food Yellow 5.
Like other azo dyes it adds colour by absorbing specific wavelengths of visible light. In the gut, intestinal bacteria can cleave the azo bond (N=N) to release aromatic amine breakdown products, including sulphanilic acid. This metabolic step is relevant to the toxicological profile of the azo dye class as a whole.
Yellow 2G was historically used in mayonnaise, soft drinks, confectionery, desserts, baked goods and ice cream to give a yellow or yellow-green tint. It is not currently permitted in the UK or EU, so no food legally sold in Britain should contain it. If encountered on an older or imported label, it may appear as E107 or Yellow 2G.
JECFA, the joint WHO and FAO expert committee on food additives, reviewed Yellow 2G three times between 1974 and 1979. In 1977 a temporary intake level of 0-0.025 mg/kg body weight was assigned, but by 1979 the committee concluded that the available data were insufficient to support any intake level at all. Key gaps included the absence of multi-generation reproductive toxicity studies and incomplete metabolism data. JECFA withdrew the specifications entirely in 1984, and Yellow 2G is not listed in the WHO/FAO General Standard for Food Additives.
JECFA assigned a temporary ADI of 0-0.025 mg/kg body weight in 1977, then withdrew it in 1979, concluding no ADI could be allocated due to insufficient data.
Multi-generation reproductive studies and embryotoxicity data were absent, and the metabolism of Yellow 2G had not been examined to a satisfactory extent, preventing a full evaluation.
JECFA formally withdrew Yellow 2G specifications in 1984; the dye is not listed in the WHO/FAO General Standard for Food Additives.
Long-term feeding studies in rats (two years) and mice (80 weeks) did not produce carcinogenic effects attributable to Yellow 2G. Minor kidney changes in rats were judged to reflect spontaneous age-related degeneration rather than treatment. However, because the overall data set was incomplete when JECFA reviewed it, the absence of cancer in these particular studies is not equivalent to a full clearance.
In a two-year rat study and an 80-week mouse study, Yellow 2G did not exert a carcinogenic effect; minor kidney changes in old rats were attributed to spontaneous age-related degeneration rather than treatment.
Short-term studies in rats (13 weeks, up to 10,000 ppm) and pigs (15 weeks, up to 500mg/kg/day) showed no serious adverse effects on growth or haematological parameters, though transient diarrhoea occurred at the highest pig doses.
Azo dyes as a class are associated with hypersensitivity reactions including urticaria (hives), angioedema and asthma in a subset of the population. The proposed mechanism involves histamine release from basophils, partly sharing a pathway with aspirin sensitivity. The reactions are described as pseudo-allergic rather than true IgE-mediated allergy. Confirmed hypersensitivity to azo dyes is estimated to affect a small fraction of the general population but is more common in people who already react to aspirin or have chronic urticaria. Yellow 2G belongs to the same structural class as the dyes involved in these reactions.
In a single-blind placebo-controlled challenge study in patients with chronic urticaria, 5.1% of those challenged reacted positively to a mixture of azo dyes, with symptoms including urticaria and angioedema.
In a study of perennial asthmatics challenged with aspirin and azo dyes, significant bronchoconstriction to azo dyes did occur, though less frequently than to aspirin; dye reactions were concluded to be an uncommon but real cause of bronchoconstriction.
Tartrazine, another azo dye, is estimated to cause hypersensitivity in 20-50% of individuals already sensitive to aspirin; Yellow 2G shares the azo bond structural feature associated with cross-reactivity.
People with aspirin sensitivity, aspirin-exacerbated respiratory disease, chronic urticaria, or a known reaction to azo dyes should be especially watchful. Because Yellow 2G is not permitted in UK or EU food, the practical risk is from imported products where local rules differ. On a label, look for E107 or Yellow 2G.
Yellow 2G is a dye that regulators removed from the permitted list not because of a specific proven harm at food-use levels, but because the safety data submitted were incomplete and no acceptable intake level could ever be established. Long-term animal studies did not find cancer, but reproductive toxicity data were missing and metabolism was insufficiently understood. The azo dye hypersensitivity concern is real but affects a minority, mainly those already sensitive to aspirin or with chronic urticaria. The picture is one of regulatory caution under data insufficiency rather than a settled finding of harm.
Yes. E107 Yellow 2G is not listed as a permitted food additive in the UK. It does not appear in the UK FSA approved additives list or in the assimilated EU Regulation 1333/2008 Annex II. No food legally sold in the UK may contain it.
JECFA, the international food additive expert committee, could not establish an acceptable daily intake because the available data were incomplete. Multi-generation reproductive toxicity studies and adequate metabolism data were never submitted. When a full evaluation cannot be completed, regulators cannot authorise use. The absence of cancer in the animal studies available did not make the overall data set sufficient.
Yellow 2G is not permitted in UK or EU food. Historically, before its withdrawal, it was used in mayonnaise, soft drinks, confectionery, desserts and baked goods. No current UK or EU food product should legally contain it.
Yellow 2G is a fully synthetic dye with no animal-derived ingredients in its composition, so it would be considered vegan on that basis. However, as with many synthetic dyes, it underwent animal testing during safety evaluations.
Last reviewed: 20 June 2026
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