Onion
ToxicOnion is toxic to dogs: organosulfur compounds oxidize hemoglobin, causing Heinz-body hemolytic anemia that shows up days after the meal, not minutes.
This food guide has not been reviewed by a veterinarian. It summarises general information from sources and should not be used to decide whether a food is suitable for an individual dog or to assess an emergency.
Check before feeding
Do not offer as a treat
There is no recommended treat portion for this hazardous item. If swallowed, contact a vet with the amount, time and product details. Do not induce vomiting yourself.
Signs and health concerns
This list includes both observable signs and conditions identified through examination or testing. It cannot establish the cause or whether an exposure is safe.
- Vomiting
- Diarrhoea
- Lethargy
- Loss of appetite
- Pale gums or mucous membranes
- Fast heartbeat
- Haemoglobin in urine
- Jaundice
More about this food
Onion poisoning is a blood problem wearing a stomach problem's clothes. Organosulfur oxidants -- n-propyl disulfide and sodium n-propylthiosulfate -- oxidize hemoglobin inside red cells; the denatured protein clumps into Heinz bodies, the spleen removes those cells, and the dog develops methemoglobinemia and hemolytic anemia. Cooking, sauteing, dehydrating and powdering do not destroy it. Powder is the worst per gram because the water is gone.
Merck puts the clinical-sign dose in dogs at 15-30 g/kg of raw onion. For a 22 lb (10 kg) dog that is roughly 150-300 g, about one to two medium onions. That sounds unreachable until you count the concentrated forms that live in an American kitchen: onion soup mix, dry onion powder in a spice rack, dehydrated minced onion, taco and chili seasoning packets, gravy mixes, French onion dip, and the onions in leftover pizza, burgers, stuffing and stew. A few tablespoons of onion powder can reach the same dose as a whole onion. Baby food used to hide onion powder too, so always read labels before sharing.
The timing is what fools people. Vomiting and diarrhea can come within hours, but Heinz bodies form inside 24 hours and peak around 72 hours, and visible anemia -- pale gums, rapid breathing, tachycardia, weakness, jaundice, port-wine or coffee-colored urine, collapse -- typically appears 3-5 days later. A dog that is bright the next morning is not cleared.
Call your veterinarian, or the ASPCA Animal Poison Control Center at (888) 426-4435 (fee applies), with the form eaten (raw, cooked, powdered), the amount and the time. Do not induce vomiting at home. Expect your vet to recheck a CBC at 24 and 72 hours to watch Heinz bodies and packed cell volume, even if your dog looks well.
Frequently asked questions
- My dog ate a burger with grilled onions. Should I worry?
- Cooking does not remove the oxidants, so the onion still counts toward the 15-30 g/kg clinical-sign dose. Estimate how much onion was on it, note your dog's weight and the time, and call your vet or the APCC at (888) 426-4435 for a dose assessment.
- Is onion powder really worse than a raw onion?
- Per gram, yes. Dehydrated onion and onion powder have the water removed, so the toxic organosulfur compounds are several-fold more concentrated by weight, and a few tablespoons of powder in a soup mix or seasoning packet can match a whole onion.
- It has been 24 hours and he seems fine. Are we in the clear?
- Not yet. Heinz bodies peak around 72 hours and clinical anemia usually appears at 3-5 days, so a normal first day means little. Have a CBC run at 24 and 72 hours and watch gum color, breathing rate and urine color through day five.