Can Dogs Eat Onions or Garlic?

Why Allium vegetables are toxic — the actual mechanism

Onions and garlic contain organosulfur compounds that damage the haemoglobin inside a dog's red blood cells through oxidative stress. The damaged cells clump into structures called Heinz bodies and are removed by the spleen faster than the body can replace them — leading to haemolytic anaemia. Garlic is roughly five times more potent gram-for-gram than onion, and cats are even more sensitive than dogs to the same mechanism.

Because the damage accumulates over time rather than hitting all at once, symptoms are often delayed — sometimes several days after a meal containing onion or garlic, which makes it easy to miss the connection.

Symptoms & timeline

Hidden sources

This is where most exposures actually happen — not from a dog eating a raw onion, but from seasoned leftovers and processed foods:

• Gravy, soup, and stock — onion/garlic powder is a near-universal base ingredient
• Boerewors, sausages, and many processed meats (check the ingredient list)
• Pizza, pasta sauce, and takeaway leftovers
• Baby food (some savoury varieties contain onion powder)
• Onion and garlic powder specifically — more concentrated than the fresh vegetable

What to do if your dog ate onion or garlic

1. Estimate the amount relative to your dog's size — a small taste of seasoned food is a different risk than a bowl of onion soup.
2. Call your vet, especially for repeated or larger exposures.
3. Watch for delayed symptoms over the following 3–5 days: pale gums, lethargy, and dark urine are the key signs to catch.
4. Blood work (a PCV/CBC) is the way vets confirm or rule out anaemia if exposure was significant.