E-numbers / Preservatives / E210
also: benzenecarboxylic acid
A preservative that stops mould, yeast and bacteria growing, added to acidic soft drinks, sauces and pickles.
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Brown Shrimp (Crangon Crangon) (98%) (Crustaceans), Salt, Preservative: Benzoic Acid, Acidity Regulator: Citric Acid
In drinks also containing vitamin C, benzoic acid can react to form benzene, an IARC Group 1 carcinogen.
30
of the 43,325 UK supermarket foods we checked declare E210 in their ingredients
That is under 0.1%, counted by its code or its name.
Counted by NutraSafe from UK supermarket ingredient lists, September 2026. How we counted
Why it’s worth knowing. In drinks also containing vitamin C, benzoic acid can react to form benzene, an IARC Group 1 carcinogen. People with aspirin or salicylate sensitivity may experience skin or breathing reactions. Children who drink large amounts of benzoate-preserved drinks may exceed the acceptable daily intake.
Benzoic acid is a simple aromatic acid that occurs naturally in cranberries, blueberries, prunes and cinnamon. The form added to food (E210) is usually produced synthetically. Its salts, sodium benzoate (E211), potassium benzoate (E212) and calcium benzoate (E213), are more soluble and more widely used in practice.
Benzoic acid works by crossing into microbial cells in its undissociated (uncharged) form. Inside the more alkaline cell interior, it releases acid, disrupting the cell's internal pH balance and interfering with its energy-producing enzyme systems. This halts growth of moulds, yeasts and some bacteria. It is most effective in acidic foods (pH below 4.5), which is why it appears mainly in fizzy drinks, vinegar-based sauces and pickled products.
Most commonly found in carbonated soft drinks and diluted fruit-flavoured drinks, pickled vegetables and olives, vinegar-based sauces and mayonnaise-style dressings, prawn cocktail sauce, and some marinated fish products. On the label it appears as 'benzoic acid', 'E210', or through its salts listed as 'sodium benzoate (E211)', 'potassium benzoate (E212)' or 'calcium benzoate (E213)'.
When benzoic acid or its salts are present in the same drink as ascorbic acid (vitamin C), they can react, especially under heat or light exposure, to produce benzene. Benzene is an IARC Group 1 carcinogen, meaning there is sufficient evidence it causes cancer in humans, in particular acute myeloid leukaemia. In 2006 the UK Food Standards Agency tested 150 beverages and detected benzene in 43 of them, with four exceeding the WHO drinking water standard of 10 parts per billion. Manufacturers have since reformulated many products to avoid the combination, but the reaction remains a reason to read labels on drinks that list both a benzoate and vitamin C.
Benzene is classified as carcinogenic to humans (IARC Group 1), with sufficient evidence it causes acute myeloid leukaemia in adults and limited evidence for other blood cancers including non-Hodgkin lymphoma and multiple myeloma.
The UK FSA detected benzene in 43 of 150 beverages tested, with four samples exceeding the WHO drinking water guideline of 10 ppb; the highest contamination found in a single product was 87.9 ppb.
Benzene forms through decarboxylation of benzoic acid in the presence of ascorbic acid, transition metal ions (iron, copper) and heat or light; the FDA first became aware of this in 1990 and asked manufacturers to reformulate their beverages.
The EFSA ANS Panel re-evaluated benzoic acid and its salts in 2016 and set an acceptable daily intake (ADI) of 5 milligrams per kilogram of body weight per day. The Panel found that in a 'brand-loyal' scenario, where toddlers or children regularly drink flavoured benzoate-preserved drinks, the ADI could be exceeded, and that additional exposure from benzoate used in other food categories could push intake two to three times above the ADI in high-level consumers. This means a child who regularly drinks several servings of benzoate-containing cordials or fizzy drinks may be getting more than the amount the regulator considers acceptable.
The EFSA ANS Panel set an ADI of 5 mg benzoic acid per kilogram body weight per day, derived from a no-observed-adverse-effect-level of 500 mg/kg/day in a four-generation reproductive study in rats with an uncertainty factor of 100.
In a brand-loyal exposure scenario, the ADI was exceeded for toddlers and children consuming flavoured drinks regularly; when carry-over from other permitted food categories was added, high-level consumers could reach two to three times the ADI.
People with aspirin or salicylate intolerance can react to benzoic acid and benzoates, experiencing hives, skin rashes, nasal symptoms, or asthma-like breathing difficulties. This is a pseudo-allergic reaction (not an immune antibody response) linked to disrupted prostaglandin pathways, the same mechanism underlying aspirin intolerance. Studies of asthmatic patients reported benzoate intolerance rates of around 11 per cent in those with asthma and 2.5 per cent in those with rhinitis. People with chronic urticaria (hives) are also at elevated risk.
Early oral provocation studies found that sodium benzoate induced urticaria and asthma in a subset of aspirin-sensitive patients, implicating a prostaglandin-mediated pseudo-allergic mechanism rather than a true IgE allergy.
Intolerance to benzoate was reported in approximately 11.5% of asthmatic patients and 2.5% of rhinitis patients in oral challenge studies.
A 2007 randomised controlled trial commissioned by the UK FSA (the McCann or 'Southampton' study) found that mixtures containing six artificial colours plus sodium benzoate were associated with increased hyperactivity in both 3-year-olds and 8 to 9-year-olds. However, because the drinks contained a mixture of colours and benzoate together, it was not possible to separate the effect of benzoate from the colours. When EFSA reviewed the evidence in 2008, it concluded the study showed limited evidence of a small effect on activity and attention in some children, but that the inconsistency between age groups and drink mixes made it impossible to attribute the effect to any individual additive. No change to the ADI for benzoate was recommended, and the EU warning label requirement that followed ('may have an adverse effect on activity and attention in children') was applied to the six colours only, not to sodium benzoate.
A randomised double-blind placebo-controlled trial found that drinks containing a mixture of six synthetic colours and sodium benzoate were associated with significantly increased hyperactivity in both 3-year-old and 8 to 9-year-old children in the general population.
EFSA AFC Panel concluded that because mixtures of additives were used, it was not possible to identify the effects of individual additives; no basis was found for changing the ADI for sodium benzoate.
An observational cross-sectional study of 475 college students found that higher sodium benzoate-containing beverage intake was significantly associated with self-reported ADHD symptoms, though the design cannot establish cause and direction of effect.
A small ex vivo study published in 2025 exposed gut microbiome samples from 24 people across four age groups to a dose ten times the ADI for 24 hours and found only minimal effects on bacterial diversity and composition. An earlier mouse study found some shifts in specific bacterial species. The human-relevance of these laboratory findings at real-world food doses is not established.
An ex vivo gut fermentation model using samples from 24 donors across infant, toddler, adult and older adult groups found that sodium benzoate at ten times the ADI had minimal effects on alpha and beta diversity, with selective reductions in Escherichia coli and increases in butyrate-producing bacteria over 24 hours.
People with aspirin intolerance or salicylate sensitivity should check labels for 'benzoic acid', 'E210', 'sodium benzoate (E211)', 'potassium benzoate (E212)' or 'calcium benzoate (E213)' and avoid products carrying any of these. Parents of children who regularly drink fizzy or flavoured drinks should be aware that heavy daily consumption of benzoate-preserved drinks may push intake above the acceptable daily intake for small children. Anyone with impaired kidney function has reduced clearance of benzoic acid and may face elevated exposure.
E210 is one of the oldest synthetic food preservatives, with a well-characterised toxicology going back decades. The main verified concern is not benzoic acid itself but the benzene it can form when combined with vitamin C in drinks, particularly under heat or sunlight. Benzene is a proven human carcinogen. Many drinks manufacturers reformulated products from the mid-2000s to remove the combination, but it has not disappeared from the market. The hypersensitivity risk is real for aspirin-sensitive people but affects a minority. The hyperactivity question remains genuinely open: the largest randomised trial (McCann 2007) used a mixture that makes it impossible to isolate benzoate's contribution. The science on gut microbiome effects at typical dietary doses is early and inconsistent. What the regulator has confirmed is that children who drink a lot of benzoate-preserved soft drinks may regularly exceed the amount considered acceptable by safety assessors.
No. Benzoic acid (E210) is approved as a food preservative in the UK and EU. It is permitted in a defined list of food categories including soft drinks, pickled vegetables, sauces and fish products, subject to maximum permitted levels.
Benzoic acid itself is not classified as a carcinogen. The concern is that in drinks containing both a benzoate preservative and vitamin C (ascorbic acid), a chemical reaction can produce small amounts of benzene, which is an IARC Group 1 carcinogen linked to leukaemia. The levels detected in some drinks in 2006 exceeded WHO drinking water standards. Many manufacturers have since reformulated to avoid this combination.
E210 appears mainly in carbonated and flavoured soft drinks, diluted squashes, vinegar-based sauces, pickled vegetables, olives, marinated fish, and some dressings and mayonnaise-style products. It is more often listed in its salt forms such as sodium benzoate (E211) or potassium benzoate (E212) than as E210 directly.
Yes. Commercially produced benzoic acid is made synthetically and contains no animal-derived ingredients. It is suitable for vegan, vegetarian, halal and kosher diets.
Last reviewed: 20 June 2026
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