Propylene Glycol — Hidden Processing Agent — Is It Vegan?
Also known as: 1,2-propanediol, E1520, PG
Vegan
No animals or animal-derived substances are involved in producing this agent.
Not required on labels
Listed as E1520 or 'propylene glycol' when used as a direct food additive.
Source
Used In
How to Avoid
Editorial Notes
Propylene glycol is not to be confused with ethylene glycol (the common automotive antifreeze, which is toxic). Propylene glycol is approved as a food additive and is GRAS in the USA. It is used in some food flavours as a carrier solvent. In e-cigarette liquids, PG is one of the two base liquids (with vegetable glycerin).
In depth
How propylene glycol is made
Propylene glycol is manufactured almost entirely by synthetic routes. The dominant industrial process starts with propylene oxide, a petrochemical derived from propylene, which is reacted with water at elevated temperature and pressure. The reaction yields propylene glycol along with smaller amounts of dipropylene and tripropylene glycol, and the fractions are separated by distillation.
A second, growing route is bio-based: glycerol, a byproduct of biodiesel production, can be converted to propylene glycol through catalytic hydrogenolysis. Several manufacturers market this version as renewable or bio-based propylene glycol. Because biodiesel feedstocks are commonly plant oils such as soybean or rapeseed, glycerol from this source is frequently plant-derived.
Neither route involves animal-derived raw materials or animal-derived processing aids at any stage, which is why propylene glycol is consistently classified as vegan. The finished substance is a clear, colorless, nearly odorless liquid with a faintly sweet taste and high miscibility with water, which makes it useful as a solvent and humectant.
Why it does not always appear on labels
When propylene glycol is added directly to a food — for example as a humectant in baked goods or icings — it must be declared in the ingredient list, appearing as 'propylene glycol' in the United States or under the E-number E1520 where the European Union permits such use.
Its most common food use, however, is indirect: it serves as a carrier solvent for flavorings and colorings. Many liquid flavor concentrates are dissolved in propylene glycol before being dosed into soft drinks, candy, baked goods, and dairy desserts. In this role it enters the product as a component of a compound ingredient, and depending on the jurisdiction and the amount involved, it may be covered by the collective term 'flavoring' rather than listed by name. This is the production-stage angle that matters for label readers: a product can contain small amounts of propylene glycol without the words appearing anywhere on the package.
From a vegan standpoint this invisibility is not a concern, since the substance itself is not animal-derived regardless of how it enters the recipe.
Regional and regulatory differences
In the United States, propylene glycol is generally recognized as safe (GRAS) by the FDA and is permitted in a broad range of food applications. In the European Union it is approved as additive E1520, but its authorized uses are narrower: it functions mainly as a carrier for flavorings, colors, and certain other additives rather than as a general-purpose direct additive, and limits apply to how much may carry over into finished foods.
One notable divergence concerns pet food. Propylene glycol is prohibited in cat food in the United States because cats are unusually sensitive to it, while it remains permitted in some dog foods. This detail is sometimes raised in animal-welfare discussions, though it does not affect the substance's vegan status.
For halal and kosher certification, propylene glycol itself is generally unproblematic because it is synthetic or plant-derived. Certifiers focus instead on what is dissolved in it — a flavor carried in propylene glycol may still contain non-kosher or non-halal components.
Products where people are surprised to find it
Propylene glycol turns up in more product categories than most consumers expect. In food, it appears in icings, some ice cream formulations, salad dressings, cake mixes, and flavored coffees and syrups, usually arriving through flavor or color carriers rather than as a named ingredient.
Outside of food, it is one of the two base liquids in most e-cigarette liquids, alongside vegetable glycerin. It is a standard humectant in cosmetics, deodorants, and skin-care products, and a common solvent in oral and topical medications. Theatrical fog machines commonly use propylene glycol mixtures to produce visible haze, and it is used as a moistening agent in some tobacco products.
It is also sold as a lower-toxicity antifreeze for situations where accidental contact with food, pets, or drinking water is possible, such as winterizing RV plumbing. This overlap is the source of the persistent 'antifreeze in food' claim: propylene glycol does have antifreeze applications, but it is chemically distinct from toxic ethylene glycol, the conventional automotive antifreeze.
Frequently asked questions
Is propylene glycol vegan?
Yes, propylene glycol is vegan. It is produced synthetically from petroleum-derived propylene oxide or from plant-based glycerol, and no animal ingredients or animal-derived processing aids are involved in either route. Concerns about this additive relate to health sensitivities in rare cases, not animal ethics.
Is propylene glycol the same as antifreeze?
No. Conventional automotive antifreeze is ethylene glycol, a different and toxic compound. Propylene glycol has low toxicity, is approved as a food additive, and is used in some lower-toxicity antifreeze products precisely because it is safer — which is where the confusion comes from.
What is E1520?
E1520 is the European Union additive number for propylene glycol. In the EU it is authorized mainly as a carrier solvent for flavorings, colors, and certain other additives, with limits on how much may end up in the finished food. When used as a direct additive it appears on labels under this number or its full name.
Is the propylene glycol in vape juice vegan?
Yes. The propylene glycol used in e-liquids is the same synthetic or plant-derived substance used in food and pharmaceuticals, so it is vegan. Vegetable glycerin, the other common e-liquid base, is plant-derived as well; the flavorings added to e-liquids are the component worth checking if you want a fully vegan product.
Why doesn't propylene glycol always appear on ingredient lists?
Because it most often enters food as a carrier solvent inside flavoring or coloring preparations rather than as a direct additive. Components of compound ingredients like flavorings can, in many jurisdictions, be covered by the collective term 'flavoring' instead of being listed individually. Since propylene glycol is vegan, this hidden presence does not affect a product's vegan status.
What is the difference between propylene glycol and vegetable glycerin?
Both are clear, viscous, slightly sweet liquids used as humectants and carriers, but they are different compounds. Vegetable glycerin is glycerol derived from plant oils, is thicker and sweeter, while propylene glycol is thinner and is made synthetically from propylene oxide or from glycerol. Propylene glycol is always vegan; glycerin is vegan only when plant-derived, as glycerol can also be sourced from animal fats.