If your dog has eaten something toxic, contact your veterinarian or an emergency animal hospital right away. Do not wait for symptoms. In the US you can also call the ASPCA Animal Poison Control Center at (888) 426-4435 or the Pet Poison Helpline at (855) 764-7661 (fees may apply).
Why
Onions and other plants in the Allium family, including leeks, chives and shallots, contain sulfur compounds that damage red blood cells. The damaged cells break apart, which can lead to a condition called hemolytic anemia.
Cooking does not make onions safe. Onion powder is especially concentrated and appears in many foods such as soups, gravies, seasoned meat and some baby foods. Effects can add up if a dog eats small amounts repeatedly, and some breeds, such as Akitas and Shiba Inus, may be more sensitive.
Symptoms to watch for
- Weakness and tiring easily
- Pale gums
- Fast breathing or a fast heart rate
- Red or brown urine
- Vomiting, diarrhea or drooling
- Signs of anemia may not appear until several days after eating onion
What to do if your dog eats it
- Contact your veterinarian, especially if your dog ate a large amount or onion powder.
- Tell your vet what was eaten and when. Blood tests may be needed over the following days.
- Do not share leftovers such as stews, pizza or stir-fries that may contain onion.
Raw, cooked or dried onion: which forms are the most dangerous?
Dried onion is the strongest form because the water has been removed. A spoonful of dehydrated onion flakes or dry onion soup mix holds far more of the harmful compounds than the same spoonful of fresh onion.
Watch for French onion dip, onion rings, meatloaf, burgers, bouillon cubes, instant noodle flavor packets and seasoning blends. Leftover pizza crusts and fried rice are common problems too. Spring onions and scallions belong to the same family and count as well. If a label says only "spices" or "seasoning" and you can't tell what is in it, leave it off your dog's plate.
How much onion causes trouble?
The Merck Veterinary Manual notes that onion poisoning is seen consistently in animals that eat more than about 0.5% of their body weight in onion at one time. For a small dog that can be a surprisingly ordinary amount of food, and smaller amounts eaten repeatedly can also add up.
This is not a safe limit. Smaller amounts eaten over several days can add up, powder is far stronger than fresh onion, and some dogs are more sensitive. Tell your vet what your dog ate and let them judge the risk.
What happens over the following days
Onion toxicity is slow. A dog may vomit or drool on the first day and then seem normal, while its red blood cells are quietly breaking down.
If the dog ate onion recently, the vet may make it vomit and give activated charcoal. After that the key tool is bloodwork. Vets look for Heinz bodies, which are clumps of damaged protein inside red blood cells, and track the red cell count for several days. Most dogs need only rest and monitoring. Severe anemia may call for oxygen or a blood transfusion. Once exposure stops, the body replaces the damaged cells and most dogs recover.
Common questions
Are onions good for dogs?
No. Onions and other plants in the Allium family, including leeks, chives and shallots, contain sulfur compounds that damage red blood cells.
Are onions bad for dogs?
Yes. Signs of poisoning to watch for: weakness and tiring easily, pale gums and fast breathing or a fast heart rate.
Are dogs allowed to have onions?
No, keep them away from your dog. If your dog eats some anyway: contact your veterinarian, especially if your dog ate a large amount or onion powder.