Which pet food ingredients are toxic to dogs and cats?
Short answer
The ingredients treated as genuinely toxic in pet food are xylitol (dangerous to dogs), onion and garlic in any allium form, propylene glycol in cat food specifically, and ethoxyquin as a preservative. Separately, by-products, added sugar, artificial dyes and BHA/BHT are quality concerns rather than toxins. Species matters: some are dangerous to cats but not dogs.
The genuinely toxic ones
- Xylitol (birch sugar, E967) — causes a rapid, dangerous blood-sugar drop and liver damage in dogs
- Onion, garlic and other alliums — damage red blood cells; cats are more sensitive than dogs
- Propylene glycol — banned in cat food in the US because it causes Heinz body anaemia in cats; permitted in dog food
- Ethoxyquin — a preservative not approved for human food, long contested in pet food
Not toxic, but a quality signal
- Unnamed animal by-products and generic 'meat meal' — the species is undisclosed
- Added sugar and caramel colour — palatants, no nutritional purpose
- Artificial dyes — added for the owner's eye, not the animal's
- BHA and BHT — contested synthetic preservatives
- Low-value fillers — corn gluten meal, wheat middlings and similar bulking ingredients
Species-specific, and why it matters
A cat is not a small dog. Cats require taurine from their diet and cannot tolerate propylene glycol; several ingredients that are unremarkable in dog food are inappropriate in cat food. Olive Detective's pet scanner asks which species you have and flags a species mismatch — for example, a dog owner scanning a cat-only formula — alongside the ingredient flags.
None of this is veterinary advice. If an animal has eaten something on the toxic list, call a vet or a poison-control line rather than an app.
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Last updated 26 August 2026.
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