Can pets eat onion, garlic, leek and chives?

If this has already been eaten, ring your vet or an animal poison control line now rather than waiting for signs to appear — for several of these the window in which treatment works closes before the animal looks unwell. Do not try to make the animal sick at home: home emetics are dangerous for corrosive and petroleum substances and for an animal already showing signs, and salt-based ones have themselves proved fatal.

By animal

What it actually does

Alliums contain organosulfur compounds that oxidise haemoglobin, forming clumps called Heinz bodies. The damaged red cells are removed by the spleen, and the anaemia that results often does not appear for several days — an animal can seem fine the evening it eats onion and be visibly ill on day three. Garlic is roughly five times more potent than onion by weight. Cooking destroys none of it, and onion powder in gravy, stock cubes, baby food and takeaway sauces is a more common route than raw onion.

How much matters

Around 15–30 g per kg of body weight in dogs produces measurable damage — a single medium onion is a meaningful dose for a small dog. Cats show effects at lower intakes.

The bit that is usually got wrong

Garlic supplements marketed for dogs as flea deterrents work on the same chemistry that causes the toxicity, and controlled evidence for the flea benefit does not exist.

Body weight decides almost everything here, so what is trivial for a 40 kg dog can matter for a 4 kg one, and a bird is smaller again. Where a real published threshold exists this page gives it; where none does, it says so rather than inventing one.

Vegetables