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Onion Poisoning In Dogs

Onion Poisoning In Dogs

Onions not only make us cry, but they also make our pets cry too!

All onions - red, yellow, white, and green - can cause onion toxicosis in your dog. It doesn’t matter whether the onion is raw or cooked - all parts of the onion, including the flesh, leaves, juice, and skin, are dangerous for your dog. Additionally, onion powder is unsafe and other forms - juiced, dehydrated, dried, and fried are risky as well.

The reason onions and other allium family plants are dangerous is because it doesn’t take a lot to cause health problems in dogs. The Allium family is quite a large family of plants with approximately 95 species of plants including garlic, shallots, leeks, chives, and scallions, not counting ornamental varieties. 5 grams of onion per kilogram body weight (0.5% of the animal's body weight) can cause toxicity in dogs.

For example, 50 grams of onion (this is only a quarter of a medium-sized onion) may not do anything for a 150 - pound mastiff, but for a 10kg, Bichons Frise or a tiny Yorkie symptoms may become apparent.

Another example, think about a 30 kg Labrador consuming 150 - 200 g of onion or onion product - that’s the size of average onion - the risk of poisoning is apparent.

One-time or sporadic ingestion of a small piece of dried onion or onion products isn’t enough to cause health concerns such as severe anemia in your dog. However, eating a plate full of sliced onions or repeated small doses over time is a cause for concern due to accumulated toxicity.

Symptoms Of Onion Poisoning

  • Black or “Tarry” stools, dark blood in feces or urine (Hematuria), or vomit.
  • Vomiting / Diarrhea
  • Nausea: This looks like drooling in dogs.
  • Abdominal Pain: Hunching over or guarding the abdomen.
  • Lethargy
  • Labored Breathing
  • Exercise Intolerance
  • Bad Breath
  • Red Tinged Urine
  • Pale Gums
  • Tachypnea, Tachycardia
  • Cold Sensitivity

Treatment Options For Onion Poisoning

  • If ingestion was in the past 1 - 2 hours or less, Vomiting may be stimulated or their stomach flush would be used to remove any undigested toxic portions.
  • Activated charcoal can be administered to decrease absorption of the toxins from the GI tract.
  • IV fluids to maintain hydration and to flush the bloodstream.
  • Severe cases may need blood transfusions until the dog’s body generate enough new, healthy erythrocytes.
  • To make up for the reduced circulation of red blood cells, supplemental oxygen may be required.

Home Remedies For Onion Poisoning

When your dog is fighting hemolytic anemia (due to onion toxicity), do not try to use any home remedies.

The home remedies for anemia in dogs start with providing their body with enough nutrients to facilitate the synthesis of RBCs.

Undoubtedly, you will have to incorporate nutrient-rich foods rich into your diet.

Ask your veterinarian for advice about a special diet for your dog.

Prevention Of Onion Poisoning

  • Keeping the onion foods, powders, plants, and supplements away from your dog is the best prevention.
  • Place the canine toxic substances in a cupboard at inaccessible locations for your pet.
  • Make aware of everyone in the household not to share their human food with pets especially if it contains onions (ex. onion rings, stir fry, burgers with onions, etc).
  • Place a suitable protective mechanism such as fences around gardens and plant beds containing onions and other allium family plants.
  • Dispose of leftovers and watch the things that get dropped on the floor since cooking scraps or groceries can be easily picked up by your dog.

Affected Breeds Of Onion Poisoning

Additional Facts For Onion Poisoning

Risk Factors:

These Susceptible traits can make certain dogs more susceptible than others.

  • Dogs with high erythrocytes reduced glutathione and potassium concentrations.
  • Diminished erythrocyte oxidative defenses (g.due to the usage of acetaminophen).
  • Zinc Deficiency
  • Treatment with xenobiotics or certain drugs (ex. Tylenol) or other compounds.
  • Dietary factors that induce erythrocyte oxidative injury(propylene glycol, propofol, sulfonamides, dl-methionine, sulfapyridine, benzocaine, large doses of vitamin K3).
  • Glucose-6-phosphate dehydrogenase deficiency.
  • Already anemic dogs.


Allium family plants contain N-propyl disulfide (an organosulfur compound) found in almost all parts. The enzyme to digest this sulfur compound is not present in dogs. What’s the big deal! You’d guess that dogs just would poop that outright? Not really.

The oxidizing agents in the plants cause oxidative hemolysis as the sulfur compound binds with the dog’s RBCs. When they undergo oxidative damage, the oxygen-carrying capacity throughout the body is hindered heavily. Oxidation of beta-93 cysteine residues present in hemoglobin forms sulfhemoglobin. Due to sulfhemoglobin's lesser solubility than hemoglobin, it precipitates, collects, and combines with the cell membrane to form specks called Heinz bodies.

This is the disclosing sign on a blood smear for hemolytic anemia and/or onion poisoning. It is similar to a rounded, purple bead above the red blood cells under microscopic view.

Now the battle begins inside the dog’s body. Heinz bodies are considered trespassers and they are attacked by the immune system. Don’t forget that these are dogs’ own RBCs that are now considered the imposters. This destruction of own RBCs is called hemolysis.

If left untreated, RBCs’ will be destroyed faster than the body can replenish and the body’s ability to provide oxygen to the tissues as well as organs is diminished. When the quantity of oxygen needed to continue organ or system functions is not provided, sooner or later, everything burgeons into a deep anemic state.


If large amounts have been ingested, Onion toxicosis may manifest within one day of consumption; however, most common clinical signs develop after a few days.

Differential Diagnoses:

This includes other common toxicoses:

  • Brassicaceous Vegetables
  • Acetaminophen
  • Propylene Glycol
  • dl - methionine
  • Benzocaine
  • Naphthalene
  • Vitamin K3
  • Zinc and Copper


When a dog consumes onion or onion products of more than half a percent of its body weight, it would be at the risk of poisoning and if left untreated, it would be fatal.


  • Blood Tests
  • Urinalysis
  • Necropsy and Histologic Findings


Mild exposure to onion or onion products has a good prognosis and the dogs will recover soon. Increased consumption of onions can be serious, particularly without appropriate treatment. When you suspect that your dog has eaten an excessive amount of onions, rush to the vet immediately even if there are no instant signs.

When To See A Vet

Contact your vet right away, if you notice any of the following:

  • If you suspect that your dog has eaten the excessive onion.
  • Excessive Vomiting and Diarrhea.

Food Suggestions For Onion Poisoning

Avoid Onions!


Even a small amount of onion in food, if given frequently, is a reason for great concern and could cause severe anemia for your pet.

Although the size, breed, age, and overall health determine the onion toxicosis levels, there is no such thing as called a safe amount of onion for the pet.

Large breed dogs that consume small amounts of onion may evade onion toxicosis better than smaller dogs. But it is better to NEVER provide onions (in any form) to dogs.

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