Can Dogs Eat Onions or Garlic?
No. Onions, garlic, leeks, and chives all contain compounds that damage red blood cells in dogs and cats — and the effect builds up over time.
Why onions and garlic are dangerous
Onions, garlic, leeks, chives, and other members of the allium family contain compounds (disulfides and thiosulphates) that cause oxidative damage to red blood cells in dogs and cats. This can lead to hemolytic anemia — a condition where red blood cells break down faster than the body can replace them. Garlic is generally considered several times more potent than onion, gram for gram, and cats are more sensitive to it than dogs, though both are at real risk from a large enough amount.
It's cumulative, not just a single-dose risk
This is one of the more important things to understand about allium toxicity: the effect builds up over time. Small amounts fed regularly — table scraps with a bit of onion or garlic seasoning, for example — can be just as dangerous over weeks as one large ingestion at once.
Forms that are toxic
All forms count: raw, cooked, powdered, and dehydrated onion or garlic are all toxic. This includes onion powder and garlic powder in seasoning blends, broths, and many prepared foods (like most seasoned rice, soups, and sauces) — check ingredient labels on anything you're tempted to share.
Signs of toxicity
Early signs (vomiting, diarrhea) can appear soon after ingestion, but the more serious red-blood-cell effects often take a few days to show up. Watch for pale gums, lethargy, loss of appetite, a rapid heart rate, rapid breathing, and dark or "port wine" colored urine — the last one is a specific sign of red blood cells breaking down and warrants an immediate vet visit.
What to do
If you know your dog or cat ate a meaningful amount of onion, garlic, or a dish seasoned heavily with either, contact your vet or an emergency animal poison control hotline — don't wait for symptoms, since the most serious effects are delayed.
This is another one for the "no safe amount, keep it out of reach entirely" list, alongside grapes and raisins and chocolate.