A synthetic humectant used to maintain moisture in semi-moist pet foods and treats, banned from cat food in the EU due to haematological toxicity in cats, yet still permitted in dog food globally — with growing questions about gut microbiome effects.
Where it's found
Semi-moist dog and cat foods — the distinctly chewy, moisture-retaining texture of many commercial dog foods and training treats is achieved with propylene glycol. Soft dental chews, rawhide alternatives, flavoured pet medications, and some wet food formulations. It is usually listed as propylene glycol on ingredient labels though it may appear within broader preservative blends.
Routes of exposure
Chronic oral ingestion as a daily component of semi-moist pet foods. Cats consuming affected products absorb propylene glycol poorly, leading to accumulation. In dogs, daily intake via a semi-moist diet as the primary food source represents the main exposure route. Children handling pet food and treats may incidentally ingest trace amounts.
Health concerns
In cats: Heinz body anaemia — oxidative damage to red blood cells — reduced red blood cell survival, and at higher doses haemolytic anaemia causing lethargy, reduced appetite, and pale mucous membranes. In dogs: propylene glycol is metabolised more efficiently but chronic high intake has been associated with gut microbiome disruption and hepatic effects in animal research. Cross-species concern exists for small dogs fed large quantities of semi-moist food as their primary diet.
Evidence
Cat toxicity is well-established mechanistically — cats lack the enzymatic capacity to metabolise propylene glycol efficiently, causing accumulation and oxidative red blood cell damage. The EU ban from cat food is based on this confirmed toxicity. Dog effects at food-grade doses are less clearly established in peer-reviewed literature; gut microbiome disruption is plausible but not definitively characterised.
Who's most at risk
Cats are uniquely susceptible due to metabolic limitations — the EU ban reflects this specific vulnerability. Small dogs consuming semi-moist food as their entire diet face higher proportional intake than larger dogs on mixed diets.
Regulatory status
RegulationBanned in cat food in the EU. Permitted in dog food in the EU, US, and UK. Listed as GRAS (Generally Recognised As Safe) for dogs by the FDA. Several premium brands have removed it voluntarily in response to consumer pressure.
How to reduce your exposure
Avoid semi-moist foods and soft treats for cats entirely. For dogs, choose dry kibble or fresh/raw diets that do not require humectants to maintain texture. When giving training treats, opt for freeze-dried single-ingredient products. Read labels — propylene glycol should be declared if present.
The nutrition connection
Cats and dogs fed fresh or raw diets avoid propylene glycol completely. For dogs, whole food diets support gut microbiome diversity that may be compromised by repeated humectant exposure. The principle parallels human nutrition: ultra-processed pet foods with synthetic texture-modifying additives are associated with poorer health outcomes in the same way ultra-processed human foods are.