Propylene glycol
A solvent and moisture-retaining additive used to carry flavours, colours and nutrients into food and drink.
What is it?
Propylene glycol (propane-1,2-diol) is a colourless, odourless, slightly viscous liquid synthesised from propylene oxide, itself derived from petroleum. It is miscible with water and most organic solvents. The body metabolises it via the same pathway as lactic acid and clears it efficiently at typical food intakes.
What does it do?
Acts as a solvent, dissolving flavourings, colours, antioxidants and other additives so they disperse evenly through a product. Also functions as a humectant, holding moisture to prevent food drying out, and as a carrier that delivers nutrients or enzymes uniformly into a formulation.
Where you will see it
Flavoured drinks and soft drink concentrates, ready-to-eat baked goods and icings, flavoured crisps and snacks, salad dressings, some confectionery coatings, and products containing emulsified colours or antioxidants. On a label it appears as 'propylene glycol', 'propane-1,2-diol', or 'E1520'.
What the science says
Metabolism and body clearance
After ingestion, propylene glycol is absorbed and converted mainly to lactic acid and pyruvate, normal intermediates in energy metabolism. At the amounts present in food, clearance is rapid and complete. Studies in animals and humans have not found accumulation at typical dietary exposure levels.
EFSA estimated the highest dietary exposure to E1520 in children at up to 23.3 mg/kg body weight per day, below the established ADI of 25 mg/kg body weight per day, indicating dietary intake does not exceed the margin considered acceptable.
Genotoxicity and cancer
Laboratory and animal studies reviewed by EFSA found no evidence that propylene glycol damages DNA or acts as a carcinogen. EFSA's 2020 re-evaluation found no genotoxicity concern. There are no IARC classifications for propylene glycol as a food additive.
EFSA's re-evaluation identified no genotoxicity concerns from the available data on propane-1,2-diol.
Reproductive and developmental toxicity
Animal studies reviewed in EFSA's 2020 re-evaluation did not identify adverse effects on reproduction or development at dietary exposure levels. The panel found no reason to restrict use on this basis.
No adverse effects in reproductive or developmental toxicity studies were identified in EFSA's re-evaluation of E1520, and exposure estimates did not exceed the ADI across population groups.
Impurity limits flagged by EFSA
EFSA's re-evaluation recommended tightening the specification limits for lead and for trace impurities including propylene oxide, mono- and di-ethylene glycol, and propylene carbonate. These are manufacturing impurities rather than effects of propylene glycol itself, but the recommendation signals that purity standards set when the additive was first authorised had not kept pace with modern analytical capabilities.
EFSA recommended lowering the maximum lead limit in E1520 specifications from 2 mg/kg and adding explicit limits for propylene oxide and glycol-related impurities.
Combined exposure with other propylene glycol sources
Propylene glycol is also used in medicines, cosmetics and some food packaging materials. EFSA noted that dietary exposure assessments for E1520 alone may underestimate total propylene glycol intake when pharmaceutical and cosmetic sources are also present, and recommended combined exposure be assessed. This is a data gap rather than a demonstrated harm.
EFSA recommended conducting combined exposure assessments for propane-1,2-diol from food additives together with dietary exposure from other authorised sources, noting the existing dietary-only assessment may underestimate total intake.
Where it stands with the regulators
Who should be careful
Propylene glycol is not a declarable allergen under UK food law. People who take certain medications (particularly metronidazole or disulfiram, which interfere with alcohol metabolism) may accumulate propylene glycol more readily; this is a pharmaceutical concern rather than a food exposure concern at normal dietary levels. Infants metabolise propylene glycol more slowly than adults, which is why it is restricted in infant foods in some formulations. Check ingredient labels for 'propylene glycol', 'propane-1,2-diol', or 'E1520' if you wish to avoid it.
The honest read
Propylene glycol is one of the most thoroughly reviewed solvents in the food additive system. EFSA completed a full re-evaluation in 2020, examined genotoxicity, reproductive toxicity, and exposure across all age groups, and found no reason to change the ADI that has been in place for many years. The main open questions are technical: tightening manufacturing impurity specs and accounting for non-food sources in cumulative exposure models. Neither is a signal of harm from the additive itself. The compound is metabolised by the same biochemical pathway the body uses for ordinary sugars. At typical food intake levels, dietary exposure sits below the acceptable daily intake even in children, who are the highest-exposure group. This is an additive where the weight of evidence is genuinely consistent rather than contested.
Related additives
Common questions
Is E1520 banned in the UK?
No. E1520 is an approved food additive in the UK under the assimilated version of EU Regulation 1333/2008. The UK Food Standards Agency lists it as authorised, and EFSA's 2020 re-evaluation found no basis for removing or restricting it.
Is propylene glycol the same as antifreeze?
Propylene glycol is used in some antifreeze formulations marketed as less toxic than ethylene-glycol-based antifreeze. The food-grade compound (E1520) is chemically identical but must meet strict purity specifications. The antifreeze association is a point of confusion: food-grade propylene glycol and industrial-grade antifreeze are not interchangeable, and the food use involves much lower concentrations acting as a solvent or humectant, not a de-icer.
What foods contain E1520?
It is most commonly found as a carrier for flavourings, colours, and antioxidants in products such as flavoured soft drinks and concentrates, baked goods, salad dressings, confectionery coatings, and flavoured snacks. It appears on labels as 'propylene glycol', 'propane-1,2-diol', or 'E1520'.
Is E1520 vegan?
Yes. Propylene glycol is produced synthetically from petroleum-derived propylene oxide and contains no animal-derived ingredients. It is considered vegan.
Sources
- EFSA ANS Panel: Re-evaluation of propane-1,2-diol (E 1520) as a food additive (PMC full text)
- UK FSA regulated products: E-1520 Propane-1,2-diol (propylene glycol)
- Approved additives and E numbers | Food Standards Agency
- Tiered intake assessment for propylene glycol in beverages, Food Additives and Contaminants Part A, 2025
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