Patent Blue V
A synthetic blue food dye used to colour sweets, drinks and some savoury products. Not approved in the US, Canada or Australia.
Can trigger IgE-mediated allergic reactions, ranging from skin rashes and nausea to anaphylactic shock in susceptible people. People with atopic conditions such as asthma, eczema or hay fever and those with known sensitivities to synthetic dyes face higher risk.
What is it?
Patent Blue V is a synthetic triphenylmethane dye, produced from petrochemical feedstocks rather than any natural source. It creates an intense sky-blue colour at low concentrations. Also sold under the names Sulphan Blue, Acid Blue 3, Food Blue 5 and CI 42051.
What does it do?
The dye molecule absorbs light in the red and yellow parts of the visible spectrum, reflecting blue back to the eye. It is water-soluble and disperses evenly through liquids and soft foods. Its colour fades fairly quickly on prolonged exposure to light.
Where you will see it
Used in Scotch eggs (to colour the coating), certain jelly sweets, blue Curacao and similar blue liqueurs, some gelatin desserts, and decorations on confectionery. It is not widely used in UK food compared with other colours. On a UK label it will appear as 'Patent Blue V' or 'E131'.
What the science says
Allergic reactions and anaphylaxis
Patent Blue V is a well-documented cause of IgE-mediated allergic reactions. Clinical reports from sentinel lymph node biopsy procedures, where the dye is injected directly, show anaphylaxis rates of roughly 0.4 to 0.5 percent. Reactions range from skin rashes and low blood pressure to cardiovascular collapse. Prior sensitisation through food or everyday products containing the dye appears to be the route by which people develop IgE antibodies that then trigger reactions on later exposures. The mechanism is not fully settled: IgE-mediated mast cell activation is the leading explanation, but direct mast cell activation without prior IgE sensitisation is also possible.
In a series of breast cancer patients undergoing sentinel node biopsy, 0.5% had allergic reactions to Patent Blue V and 0.4% experienced anaphylaxis specifically, characterised by cardiovascular and cutaneous symptoms with poor response to ephedrine.
Anaphylaxis to Patent Blue V in a surgical series showed incidence of any reaction at 0.1 to 2.8 percent, with severe anaphylactic shock at approximately 0.06 percent; most cases are IgE-mediated mast cell activation.
Genotoxicity: open questions remain
The 2013 EFSA food additive re-evaluation found no evidence of genotoxicity using in vivo micronucleus and comet assays, and the 2021 human lymphocyte study also found no significant genotoxic effects. However, the 2024 EFSA feed additive renewal assessment identified a specific data gap: no adequate data exist on the potential of Patent Blue V to cause numerical chromosomal damage (aneugenicity). EFSA's FEEDAP Panel stated it could not rule out genotoxicity on this basis and recommended minimising user exposure. This gap applies specifically to a feed-use renewal application and does not overturn the 2013 food-use conclusion, but it is an unresolved question.
EFSA's 2013 food additive re-evaluation concluded that Patent Blue V at purity above 90% showed no genotoxic concern based on negative in vivo micronucleus and comet assay results.
A 2021 study in human peripheral lymphocytes found no significant genotoxic or cytotoxic effects from Patent Blue V, though the authors noted further testing with different endpoints would be needed.
EFSA's 2024 feed additive renewal assessment found the potential for numerical chromosomal damage (aneugenicity) had not been adequately investigated and concluded genotoxicity could not be ruled out, recommending renewal authorisation not be granted.
Exposure in children may exceed the ADI at maximum permitted levels
When EFSA modelled dietary exposure in 2013, it found that at the maximum permitted use levels set in EU law, high consumers among toddlers and children could exceed the ADI of 5mg per kg body weight per day. At maximum reported actual use levels in food products, exposure for all population groups stayed below the ADI. This means the margin is tighter for young children who eat a lot of brightly coloured sweets and drinks.
At maximum permitted use levels, dietary exposure estimates for high consumers among toddlers and children exceeded the ADI of 5mg/kg bw/day; at maximum reported actual use levels, all population groups remained below the ADI.
Not approved in the US, Canada or Australia
Patent Blue V has never been approved as a food colour by the US FDA, and is also not permitted in Canada or Australia. The primary grounds cited across these jurisdictions are the allergic reaction risks and insufficient evidence of full safety. It remains permitted in the UK, EU and Norway under specific conditions.
Patent Blue V is not on the US FDA list of colour additives approved for use in food. It is similarly not on Canada's List of Permitted Food Colours or Australia's permitted food additives list.
Where it stands with the regulators
Who should be careful
People with a history of reactions to synthetic food dyes or with atopic conditions (asthma, eczema, hay fever) face a higher risk of allergic reactions. Those with aspirin intolerance may also be more sensitive. On a UK label, look for 'Patent Blue V' or 'E131' in the ingredients list.
The honest read
The primary concern with Patent Blue V is well-documented: it can cause IgE-mediated allergic reactions, including anaphylaxis in rare cases, most often identified through its medical use in surgical procedures. The food exposure route is real given the dye is used in everyday products and people can be sensitised through contact with it in food, cosmetics and textiles before ever reacting. The genotoxicity picture is not completely settled: the 2013 food-use evaluation and a 2021 human cell study found no significant signals, but a 2024 EFSA review for a related application flagged that potential chromosome-number damage had not been adequately tested. Whether that gap matters at the concentrations people consume through food is an open question, not a resolved one. E131 is not a heavily used dye and most people in the UK will encounter it rarely, but the science on hypersensitivity is real and the regulatory gap on aneugenicity has not been closed.
Related additives
Common questions
Is E131 banned in the UK?
No. E131 Patent Blue V is approved for use as a food colour in the UK under the assimilated version of EU Regulation 1333/2008, confirmed as authorised in England, Scotland and Wales. It is not approved as a food colour in the US, Canada or Australia.
Can Patent Blue V cause an allergic reaction?
Yes. Clinical evidence from medical use of the dye documents IgE-mediated allergic reactions including anaphylaxis, with reaction rates in exposed patients of around 0.4 to 0.5 percent. People with atopic conditions such as asthma or eczema, or with known sensitivities to synthetic dyes, are considered higher risk. Sensitisation can occur through previous exposure via food, cosmetics or textiles.
What foods contain E131?
E131 is not widely used in UK food. It appears in some Scotch egg coatings, certain jelly sweets, blue Curacao and similar blue liqueurs, some gelatin desserts, and confectionery decorations. It will be listed as 'Patent Blue V' or 'E131' in the ingredients.
Is E131 vegan?
Patent Blue V is a synthetic dye derived from petrochemical sources and does not itself contain animal products. However, the foods it appears in, such as Scotch eggs or certain gelatin-based sweets, are often not vegan. Check the full ingredient list of any product.
Sources
- EFSA ANS Panel, Scientific Opinion on the re-evaluation of Patent Blue V (E 131) as a food additive, EFSA Journal 2013;11(3):2818
- EFSA FEEDAP Panel, Assessment of the feed additive consisting of Patent Blue V for renewal of its authorisation, EFSA Journal 2024
- UK FSA Approved Additives and E Numbers list
- UK FSA Regulated Products database: E-131 Patent Blue V
- Case report: Atypical anaphylactic reaction to Patent Blue V dye during breast cancer surgery, Frontiers in Oncology 2022
- Anaphylaxis to Patent Blue V (clinical aspects), PubMed
- Investigation of the genotoxic effects of patent blue V (E131) in human peripheral lymphocytes and in silico molecular docking, Drug and Chemical Toxicology 2021
- Norwegian food additives regulation (forskrift 2011-06-06-668), Lovdata - Annex II lists E 131 Patentblå V as a permitted food colour
- CFIA Food Colours page confirming Patent Blue V is not on Canada's list of permitted food colours
- Patent Blue V, Wikipedia
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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