also: FD&C Red No. 4 · Scarlet GN · Food Red 1 · C.I. 14700
A synthetic red azo dye once used to colour cherries and sweets. Not permitted as a food additive in the UK or EU.
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Long-term animal feeding studies found adrenal gland and urinary bladder lesions.
Why it’s worth knowing. Long-term animal feeding studies found adrenal gland and urinary bladder lesions. JECFA repeatedly postponed its safety decision and never set a daily intake limit, concluding the evidence was insufficient to declare it safe for food use. It is not on the UK list of approved food additives, so you will not normally see this E number on a UK label.
Ponceau SX is a synthetic azo dye, also known as Scarlet GN and FD&C Red No. 4. It carries the chemical name disodium 3-[(2,4-dimethyl-5-sulfonatophenyl)hydrazinylidene]-4-oxonaphthalene-1-sulfonate. Like other azo dyes, it produces its red colour through nitrogen-nitrogen double bonds that absorb certain wavelengths of light. It is one of several related Ponceau dyes; it is distinct from E124 (Ponceau 4R), which remains permitted in the UK with restrictions.
Used historically as a food colourant to produce a red or scarlet appearance in processed foods. Azo dyes in the gut are metabolised by intestinal bacteria, which possess enzymes (azoreductases) that can cleave the azo bond, releasing aromatic amine compounds as metabolites.
Ponceau SX is not permitted in UK or EU food and should not appear in any food sold in Great Britain or Northern Ireland. It was historically used in sweets and as a colourant for maraschino cherries, which regulators treated as decorative rather than food items. It may still appear in some foods from countries where it remains permitted; the Canadian Food Inspection Agency lists it as a permitted food colour in Canada, with permitted foods and conditions set out in the separate Health Canada List of Permitted Food Colours. On an ingredient label it would appear as E125 or as Ponceau SX.
A seven-year feeding study in female beagle dogs at high dietary doses found moderate to marked atrophy of the outer layer of the adrenal gland (the zone glomerulosa) in all test animals, along with adrenal adenomas at the highest dose. The same study found haemorrhagic streaks and blood-filled projections in the urinary bladder of all surviving animals after six months. These were the findings that informed regulators' decisions not to establish a safe daily intake.
Seven-year dog feeding study found marked atrophy of the adrenal gland's zone glomerulosa in all animals at both dose levels (10,000 and 20,000 ppm in diet), with adrenal cortical adenomas at the highest dose.
Haemorrhagic streaks and blood-filled mucosal projections in the urinary bladder of all test animals surviving more than six months at both dose levels in the dog feeding study.
IARC evaluated Ponceau SX in 1975 and again in 1987. Animal studies by oral administration in mice, rats and dogs, and by injection in mice and rats, did not show evidence of a carcinogenic effect. IARC placed it in Group 3, meaning it cannot be classified as to its carcinogenicity to humans, due to inadequate evidence in both animals and humans.
Oral studies in mice, rats and dogs did not indicate a carcinogenic effect. IARC classified Ponceau SX as Group 3: not classifiable as to carcinogenicity to humans. The Volume 8 (1975) page on inchem.org explicitly records the subsequent evaluation as 'Suppl. 7 (1987) (p. 70: Group 3)'.
The Joint FAO/WHO Expert Committee on Food Additives evaluated Ponceau SX across multiple meetings from 1959 to 1977 and each time postponed its decision, declining to set an acceptable daily intake. The committee's specifications for the dye were formally withdrawn in 1984, signalling that no basis for a safe level in food had been found.
JECFA evaluated Ponceau SX in 1959, 1964 and 1977 and each time returned a postponed decision, never establishing an acceptable daily intake. Specifications were withdrawn in 1984.
Like other azo dyes, Ponceau SX can be reduced by gut bacteria to produce aromatic amine compounds. The JECFA monograph identified metabolites including aminohydroxynaphthalenesulfonic acid derivatives. Some aromatic amines produced by azo dye breakdown are known or suspected to be toxic, though whether the specific metabolites from Ponceau SX pose a meaningful risk at former food-use levels was not formally resolved.
Ponceau SX undergoes bacterial reduction in the intestine, producing metabolites including amino-hydroxynaphthalene derivatives, as identified in the JECFA toxicological monograph.
Gut bacteria with azoreductase activity are widespread in the human intestinal microbiome and cleave the azo bond of food dyes, producing aromatic amine metabolites.
Because E125 is not authorised in UK and EU food, encountering it in a product sold in Great Britain is itself a labelling or compliance issue. Anyone buying imported foods, particularly from Canada or some Asian markets, should check ingredient lists for E125 or Ponceau SX. People who experience reactions to azo dyes more broadly may also react to related permitted dyes (such as E124).
E125 is one of the cleaner-cut cases in food additive regulation: it is not that regulators weighed the evidence and found it acceptable, but that they evaluated it repeatedly and could not establish that any level was safe for food use. The animal findings, particularly the adrenal and bladder effects in the long-term dog study, were the sticking point. The dye was quietly retired from both sides of the Atlantic and from the EU in the 1970s and 1980s. IARC's Group 3 classification means the available animal data did not show outright carcinogenicity, but Group 3 is not a clearance: it means the question was not answered to the standard required. The fact that you can still buy it as a cosmetics or laboratory reagent, but not put it in food, reflects where regulators drew the line.
Yes. E125 (Ponceau SX) is not on the UK FSA register of authorised food additives and is absent from the permitted colours list under assimilated EU Regulation 1333/2008. Using it in food sold in Great Britain would be a legal breach. It was no longer on the EU permitted list by 1976.
JECFA (the joint FAO/WHO food safety committee) evaluated Ponceau SX in 1959, 1964 and 1977 and each time declined to set an acceptable daily intake, citing insufficient safety data. Long-term animal studies had found adrenal gland and urinary bladder lesions. The committee formally withdrew its specifications in 1984, and regulators on both sides of the Atlantic removed the dye from approved food use.
None that are legally sold in the UK or EU. It was historically used in sweets and as a colourant for maraschino cherries. The Canadian Food Inspection Agency lists Ponceau SX as a permitted food colour in Canada; specific permitted foods and conditions are in the Health Canada List of Permitted Food Colours. Check labels for E125 or Ponceau SX on any imported products.
Ponceau SX is a fully synthetic coal-tar derived azo dye and contains no animal-derived ingredients. However, it is not authorised for food use in the UK or EU, so the vegan question is largely academic for shoppers here.
Last reviewed: 20 June 2026
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