Formic acid
A naturally occurring acid used as a preservative in animal feed. It is not a permitted food additive in the UK or EU for human food.
E236 is not authorised for use in food sold in the UK or EU. If you see it listed as an ingredient in a product on UK shelves, that product may not comply with food law.
What is it?
Formic acid (also called methanoic acid, HCOOH) is the simplest carboxylic acid. Its name comes from the Latin for ant: red wood ants produce it in concentrations up to 60% in their venom glands and spray it as a defence. It also occurs naturally at low levels in some fruits such as pineapples, apples and kiwis, and in stinging nettles. Commercially, it is manufactured by reacting methanol with carbon monoxide. Formic acid is a normal metabolic intermediate in the human body, eventually broken down to carbon dioxide.
What does it do?
In preservation applications, formic acid inhibits the growth of bacteria, yeasts and moulds by penetrating microbial cell membranes and lowering intracellular pH, disrupting vital enzyme processes. It lowers the overall pH of a product, creating an environment hostile to spoilage organisms. The same mechanism makes it effective as a silage preservative: it promotes lactic acid fermentation and suppresses butyric acid formation in animal feed crops.
Where you will see it
Formic acid is widely used in animal feed and silage production across Europe. It is also used industrially in leather tanning and textile processing. It is not permitted in food produced for human consumption in the UK or EU, so it should not appear on ingredient labels of food sold here. If a product does list it as E236 or formic acid, that is a labelling anomaly worth checking with the manufacturer or reporting to the relevant food safety authority.
What the science says
Regulatory status in the UK and EU
Formic acid does not appear in Annex II of the UK's assimilated version of EU Regulation 1333/2008, the definitive list of additives permitted in food for human consumption. The E-number sequence in that list jumps from E235 (Natamycin) to E239 (Hexamethylene tetramine), with E236 absent. The same is confirmed in the EU's own consolidated text of Regulation 1333/2008 (EUR-Lex, June 2024): E235 is followed directly by E239 in Part B of Annex II, with no entry for E236, E237 or E238. The UK FSA approved-additives list similarly contains no entry for E236. It was also absent from the UK Preservatives in Food Regulations 1989. There is no published EFSA re-evaluation opinion on formic acid as a human food additive.
E236 is not listed in Annex II of the assimilated UK version of EU Regulation 1333/2008. The additive sequence skips from E235 to E239, with no entry for formic acid or its formate salts (E237, E238).
The consolidated EU text of Regulation (EC) No 1333/2008 (EUR-Lex, version 02 June 2024) lists no entry for E236, E237 or E238 in Annex II Part B. The sequence runs from E235 (Natamycin) to E239 (Hexamethylene tetramine).
The UK Food Standards Agency approved-additives list contains no entry for E236 formic acid.
The Preservatives in Food Regulations 1989 (SI 1989/533) list permitted preservatives in Schedule 1; formic acid and its formate salts do not appear.
JECFA toxicology evaluation
The Joint FAO/WHO Expert Committee on Food Additives (JECFA) has evaluated formic acid on more than one occasion. An early assessment set a provisional acceptable daily intake of 0-3 mg/kg bodyweight; a later assessment reported 0-5 mg/kg bodyweight. In both cases the committee noted that long-term toxicity data were incomplete and that the ADI was conditional or provisional. In animal studies, higher doses produced methaemoglobinaemia and enzyme inhibition, though no cumulative toxic effects were identified at the assessed intake levels.
JECFA established a provisional acceptable daily intake of 0-3 mg/kg bodyweight for formic acid, based on available biochemical studies and its role as a normal metabolic intermediate. Long-term toxicity data were acknowledged as lacking.
A later JECFA assessment reported a conditional ADI of 0-5 mg/kg bodyweight and noted the committee could not set an unconditional ADI because long-term animal toxicity studies were absent. It recommended additional metabolism studies in humans.
In animal studies, sodium formate caused methaemoglobinaemia at oral doses around 50 mg/kg in dogs. At very high doses (3,000-4,000 mg/kg) toxic effects including heart congestion were observed. No cumulative effects were noted at lower doses.
Use in animal feed
EFSA has assessed formic acid specifically as a preservative and acidifier in animal feed and drinking water for all animal species, concluding it is effective and poses no safety concern to animals at recommended use levels. This is entirely separate from any assessment for human food use. The primary commercial application of formic acid is in silage and fishmeal preservation.
EFSA's Panel on Additives and Products or Substances used in Animal Feed concluded that formic acid is safe for use in feed for all animal species and categories at maximum proposed dose levels, and that residues in animal products (meat, milk, eggs) do not raise a concern for consumers.
Formate toxicity at high doses (not relevant to food additive use)
Formate is the toxic metabolite responsible for the severe effects of methanol poisoning. At high accumulation it inhibits cytochrome c oxidase, disrupting mitochondrial energy production, and causes an anion-gap metabolic acidosis. The retina and optic nerve are particularly vulnerable. These toxic mechanisms operate at formate concentrations far above any conceivable food additive exposure; they are relevant when methanol is ingested in significant quantity, not from dietary formic acid in the trace amounts found naturally in food.
Formate inhibits cytochrome c oxidase, the terminal enzyme of the mitochondrial electron transport chain. This mechanism underlies the retinal toxicity and metabolic acidosis seen in methanol poisoning.
Where it stands with the regulators
Who should be careful
Because E236 is not authorised for human food in the UK or EU, encountering it on an ingredient label would be unusual. Anyone who sees it listed should check with the manufacturer. There is no specific population group for whom avoidance is separately recommended in a food-additive context, since there is no legal food use to avoid.
The honest read
E236 carries an E-number, which leads many secondary websites to describe it as an approved EU food additive. It is not. The definitive UK legal text (the assimilated version of EU Regulation 1333/2008, Annex II) skips from E235 to E239 with no entry for formic acid or its formate salts. The EU's own consolidated text of the same regulation (EUR-Lex, June 2024) confirms the same gap. The FSA approved-additives page contains no entry for it either. Its main regulated use is in animal feed under separate feed additive rules, where EFSA has assessed it and found it effective and without concern for animals. For human food, the JECFA assessments from the 1960s set conditional acceptable daily intakes but noted absent long-term toxicity data, and no subsequent EU or UK re-evaluation for human food use has followed. The picture is therefore: not authorised, not evaluated for modern human food standards, and in practice not present in UK food products.
Related additives
Common questions
Is E236 banned in the UK?
It is not on the UK or EU permitted-additives list for human food. The UK's assimilated version of EU Regulation 1333/2008 (Annex II) does not include E236: the list goes from E235 to E239 with no entry in between. The EU's own consolidated text of the same regulation confirms the identical gap. It was also absent from the Preservatives in Food Regulations 1989. Whether this is described as 'banned' or 'never authorised' is a technical distinction: the practical result is the same: it cannot legally be used as a food additive in products for human consumption sold in the UK.
Why does E236 have an E-number if it is not permitted?
E-numbers are designations assigned to substances that have been evaluated for potential use as food additives, not automatic proof that a substance is currently authorised. E236 was assigned to formic acid during earlier review processes, but it was never added to the positive list in Annex II of Regulation 1333/2008 for human food. The E-number therefore identifies the substance but does not indicate approval.
What foods contain E236?
No UK or EU food for human consumption should legally contain added E236. It is used in animal feed and silage. Formic acid does occur naturally at trace levels in some fruits (pineapple, apple, kiwi) and in stinging nettles, but these are not additive uses.
Is E236 vegan?
The substance itself is synthetic (produced industrially from methanol and carbon monoxide), so no animal-derived material is involved in its manufacture. However, since it is not a permitted food additive in the UK or EU, the question of whether it appears in food here does not arise in practice.
Sources
- UK legislation.gov.uk: Regulation (EC) No 1333/2008 on food additives, Annex II (version 28 June 2024)
- EUR-Lex: Consolidated text of Regulation (EC) No 1333/2008, CELEX:02008R1333-20240602 (2 June 2024)
- UK Food Standards Agency: Approved additives and E numbers
- UK legislation.gov.uk: The Preservatives in Food Regulations 1989 (SI 1989/533), Schedule 1
- JECFA Monograph 265: Formic acid (WHO Food Additives Series 5)
- JECFA Monograph 003: Formic acid (FAO Nutrition Meetings Report Series 38a)
- EFSA: Scientific Opinion on the safety and efficacy of formic acid when used as a technological additive for all animal species (EFSA Journal 2014;12(7):3827)
- Liesivuori J, Savolainen H. Methanol and formic acid toxicity: biochemical mechanisms. Pharmacology and Toxicology, 1991
- Wikipedia: Formic acid
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