A powerful oxidising gas, historically used to bleach flour. Not a permitted food additive in the UK or EU.
Chlorine dioxide is not authorised for use in UK or EU food. Products sold claiming to contain or generate it as a dietary supplement have been subject to health warnings from food safety regulators.
What is it?
Chlorine dioxide (ClO2) is a yellowish-green gas with strong oxidising properties. It is produced industrially and used in water purification, wood-pulp bleaching, and surface disinfection. In food contexts it belongs to the flour treatment agent category but is not currently authorised in the UK or EU.
What does it do?
As an oxidising agent it reacts with pigments in flour to whiten it (bleaching) and modifies gluten proteins to alter dough handling properties. At low concentrations it can also act as a broad-spectrum antimicrobial by disrupting cell membranes and oxidising proteins in micro-organisms.
Where you will see it
No longer used in UK or EU food production. Historically appeared as a flour treatment agent in white cake flour and some industrial baked goods in countries where it remains permitted, such as the United States. It does not appear on UK or EU ingredient labels as a food additive. Products marketed as 'Miracle Mineral Solution' or 'MMS' generate chlorine dioxide when mixed and have been sold as dietary supplements, but these are not food products and have attracted explicit safety warnings from UK and EU regulators.
What the science says
Formation of toxic by-products: chlorite and chlorate
When chlorine dioxide reacts with food components or water it breaks down to form chlorite and chlorate ions. Both have been linked to adverse effects on red blood cells at higher exposures, and chlorate is under ongoing regulatory scrutiny as a contaminant in fruit and vegetables treated with chlorinated water.
Chlorate, a breakdown product of chlorine dioxide, has been found as a residue in fruit and vegetables treated with chlorinated wash water. EFSA concluded that current dietary exposure to chlorate may exceed the tolerable daily intake for some population groups, including infants.
Chlorite, another breakdown product, causes haemolytic anaemia in animal studies at sufficient doses by oxidising haemoglobin.
Not authorised in UK and EU food
Chlorine dioxide has never been included in the EU positive list of permitted food additives (Annex II of Regulation 1333/2008). The UK carried this prohibition into retained law after Brexit. The flour bleaching uses that once existed in some countries were not brought into the EU system because regulators were not satisfied that the safety case had been established for food-grade use.
Chlorine and chlorine dioxide are not permitted flour treatment agents in the European Union. Use of chlorine, bromates, and peroxides for flour treatment is prohibited under EU food additives legislation.
The UK Bread and Flour Regulations 1998 prohibit the use of flour bleaching agents including chlorine gas and chlorine dioxide in bread and flour sold in the UK.
Dangers of 'Miracle Mineral Solution' containing chlorine dioxide
Chlorine dioxide has been marketed in some countries as a dietary supplement under names including 'Miracle Mineral Solution' (MMS) and 'CD Protocol'. Regulators in the UK, US, and EU have explicitly warned against consuming these products, which generate chlorine dioxide when mixed. Reported adverse effects in people who consumed them include severe nausea, vomiting, diarrhoea, and dangerous drops in blood pressure.
The UK Food Standards Agency has issued warnings that drinking solutions containing sodium chlorite that generate chlorine dioxide is potentially dangerous and the products are not authorised food additives.
The US FDA warned that Miracle Mineral Solution products release chlorine dioxide and that drinking them can cause severe vomiting, diarrhoea, dangerous drops in blood pressure, and acute respiratory failure.
Where it stands with the regulators
Who should be careful
There is no authorised food use of chlorine dioxide in the UK or EU, so it should not appear in any legally sold UK food product. Anyone who has purchased a product described as 'Miracle Mineral Solution', 'MMS', 'CD Protocol', or any supplement claimed to generate chlorine dioxide should not consume it. The UK FSA has explicitly warned against these products.
The honest read
Chlorine dioxide sits in an unusual position: it has genuine and long-established industrial uses in water treatment and disinfection, and a permitted food use in the US as a flour bleaching agent, but it has never been authorised in UK or EU food and the safety case for dietary exposure has not been established to the satisfaction of European regulators. The concern about its breakdown products, particularly chlorate and chlorite, is real and backed by regulatory review. Separately, the 'Miracle Mineral Solution' episode represents a more acute public health issue, with documented cases of serious harm. The science on low-level dietary exposure from flour treatment (as used in the US) is less settled, but that question is moot for UK consumers since the use is simply not permitted here.
Related additives
Common questions
Is E926 banned in the UK?
Yes, in practical terms. Chlorine dioxide is not included in the UK's list of approved food additives (inherited from EU Regulation 1333/2008). This means no food manufacturer can legally use it as a food additive in the UK. The UK Bread and Flour Regulations 1998 also specifically prohibit it as a flour treatment agent.
Why is bleached flour banned in the UK but allowed in the US?
The EU and UK operate a 'positive list' system: only additives that have been reviewed and approved may be used in food. Chlorine dioxide was never submitted for EU approval or was not accepted onto the list. The US FDA takes a different approach and permits chlorine dioxide in flour at low levels. UK flour is whitened naturally over time through oxygen exposure rather than chemical bleaching.
What foods contain E926?
None legally sold in the UK or EU. In the US, some commercial cake flours and white flours may be treated with chlorine dioxide. It does not appear on UK ingredient labels.
Is E926 vegan?
Chlorine dioxide itself is an inorganic compound with no animal-derived ingredients. However, since it is not a permitted food additive in the UK or EU, the vegan question is not practically relevant for UK shoppers.
Sources
- UK FSA: Approved additives and E numbers
- UK FSA: Miracle Mineral Solution and sodium chlorite solutions
- EU Regulation 1333/2008 on food additives (Annex II positive list)
- EFSA CONTAM Panel opinion on chlorate in food (2015), EFSA Journal
- US FDA: Danger: Don't Drink Miracle Mineral Solution or Similar Products
- The Bread and Flour Regulations 1998 (SI 1998/141)
- US EPA Integrated Risk Information System: Chlorite
- Wikipedia: Flour bleaching agent
- UK FSA regulated-products data register: E926 (returns no authorisation record)
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