✓ Reviewed against PDSA, Blue Cross & Animal PoisonLine guidance · Last reviewed: 2026-04
Can dogs eat onions?
The full picture
Onions belong to the Allium family, along with garlic, leeks, shallots, chives, and spring onions. They contain organosulfoxides — sulphur compounds that damage dogs' red blood cells, causing a condition called haemolytic anaemia. Cooking, drying, or powdering does not destroy these compounds; onion powder is actually the most concentrated form, which is why processed foods are a significant source of accidental exposure. Damage builds up over time, so symptoms may not appear for several days after eating onions, and repeated small exposures can cause anaemia just as serious as one big meal. Roughly 15–30 g of onion per kg of body weight can cause toxicity — meaning a 10 kg dog only needs to eat a slice or two of a medium onion for a problem.
If your dog has already eaten onions
- Call your vet if your dog has eaten more than a lick of onion or onion-containing food
- If your vet is closed, call the Animal PoisonLine on 01202 509000
- Try to identify exactly what was eaten — onion powder is much more potent than raw onion by weight
- Do NOT induce vomiting unless your vet instructs you to
- Note that symptoms may take days to appear — don't assume your dog is OK just because they seem fine tonight
Information to have ready when you call:
- What was eaten (raw onion, cooked, onion powder, onion-containing dish)
- Approximate amount
- Time of ingestion
- Your dog's weight
- Whether this was a one-off or regular exposure
Risks to watch for
- Haemolytic anaemia (damage to red blood cells)
- Weakness, lethargy, reduced appetite
- Pale gums
- Rapid breathing
- Dark red or orange urine (a late sign)
- Elevated heart rate
- Vomiting and diarrhoea
What to watch for — and when
[{'when': 'Within 24 hours', 'signs': 'Stomach upset — vomiting, diarrhoea, loss of appetite'}, {'when': '1–3 days', 'signs': 'Lethargy, weakness, reluctance to exercise'}, {'when': '3–7 days', 'signs': 'Signs of anaemia — pale gums, rapid breathing, dark urine'}]
Hidden sources to check
- Gravy and gravy granules (almost always contain onion)
- Stuffing mixes (onion is the main flavour)
- Baby food (check labels — many contain onion)
- Soups, stocks, and stock cubes
- Shop-bought minced meat dishes (shepherd's pie, bolognese, cottage pie)
- Tomato-based pasta sauces and pizza sauces
- Hummus, pesto, chutneys, pickles
- Chinese, Indian, and Thai takeaway dishes
- Garlic bread, onion rings, bhajis
- Many commercial pet treats imported from other countries — read labels
Breed-specific notes
- Japanese breeds (Akita, Shiba Inu) are reportedly more sensitive to Allium toxicity — be especially cautious.
- Smaller dogs reach toxic doses on much smaller amounts.
Safe portion size
None. No form of onion is safe.
Safer alternatives
- Plain cooked carrots
- Green beans
- Cucumber
- Plain cooked chicken
Cat owners should note that onions are equally toxic to cats — cat food safety at CatEatIt covers which foods affect both species.
Common questions
My dog ate a bit of food with onion in the sauce — should I worry?
What about spring onions, shallots, leeks, and chives?
Is cooked onion safer than raw?
How much onion is toxic?
My dog ate onion days ago and is fine — are they clear?
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