Onion and Garlic Toxicity
Allium toxicosis
Also known as: Allium toxicosis, Onion poisoning, Garlic poisoning
CatDogUrgency: High
Allium toxicosis
Also known as: Allium toxicosis, Onion poisoning, Garlic poisoning
In short
Onion and garlic ingestion causes oxidative damage to red blood cells in dogs and cats, leading to Heinz body anemia, weakness, and potentially life-threatening kidney damage.
TL;DR. Ingesting onions, garlic, or other Allium species causes oxidative damage to your pet's red blood cells, leading to a serious form of anemia that requires prompt veterinary attention.
Even cooked dishes containing onions or garlic can pose a severe toxic threat to cats and dogs.
Onion and garlic toxicity, scientifically known as Allium toxicosis, is a dangerous poisoning that occurs when dogs or cats ingest plants in the Allium genus. This plant family includes not only onions and garlic but also leeks, chives, and shallots. Whether raw, cooked, dehydrated, or powdered, these plants contain toxic organosulfur compounds that pets cannot safely metabolize.
When a pet digests these compounds, the toxins enter the bloodstream and cause oxidative damage to the red blood cells. Red blood cells are responsible for carrying oxygen from the lungs to the rest of the body using a protein called hemoglobin. The oxidative stress caused by Allium species damages this hemoglobin, causing it to clump together. These clumps are visible under a microscope and are called Heinz bodies. Additionally, the damage deforms the cell membrane, creating fragile, distorted cells known as eccentrocytes.
Because these damaged red blood cells are abnormal, the pet's body identifies them as defective and prematurely destroys them in a process called hemolysis. If the rate of destruction exceeds the bone marrow's ability to produce new red blood cells, the pet develops hemolytic anemia. This lack of healthy red blood cells deprives vital organs of oxygen, which can lead to systemic illness, organ failure, and in severe cases, death.
Any exposure to plants of the Allium family can trigger toxicosis. This includes common kitchen ingredients like yellow, red, and white onions, garlic cloves, garlic powder, onion powder, chives, shallots, and leeks. Even wild varieties can pose a threat to pets that spend time outdoors. According to a leading veterinary nutrition manual:
"Wild onions (A. validum & A. Canadense) and wild garlic (A. ursinum) have caused haemolytic anaemia in horses and ruminants (Lee K-W et al. 2000) and are potentially toxic for dogs and cats as well."
Both dogs and cats are highly susceptible to this toxicity. Cats are particularly sensitive due to the unique structure of their hemoglobin, which makes their red blood cells more vulnerable to oxidative damage. However, dogs also have a long-documented sensitivity to these plants:
"It has been known since 1930 that dogs are very sensitive to onions (Allium spp) whether raw, cooked or dehydrated."
While there are no specific breed predispositions listed in standard records, individual genetic variations can significantly increase a pet's vulnerability. Specifically, some dogs carry a hereditary trait that alters their red blood cell chemistry, making them far more susceptible to the toxic compounds in onions and garlic:
"Dogs with hereditary high erythrocyte concentrations of reduced glutathione and potassium appear to be more sensitive to onion and garlic poisoning (Yamato O and Maede Y 1992)."
Symptoms of Allium toxicosis do not always appear immediately. It often takes several days after ingestion for the oxidative damage to cause a noticeable drop in red blood cells. The clinical signs reflect both the destruction of red blood cells and the body's struggle to compensate for reduced oxygen delivery.
Pale or yellow-tinted gums are a key indicator of severe anemia and jaundice caused by red blood cell destruction.
Your vet will begin with a thorough physical examination, paying close attention to your pet's gum color, heart rate, and breathing effort. If you suspect or know your pet ate onions or garlic, share this timeline with your vet immediately.
To confirm a diagnosis of Allium toxicosis, your vet will perform specific laboratory tests:
Under a microscope, vets look for Heinz bodies and eccentrocytes to confirm Allium poisoning.
There is no specific antidote for onion or garlic poisoning. Treatment focuses on preventing further absorption, supporting the pet's oxygen levels, protecting the kidneys, and managing oxidative stress.
If the ingestion occurred within the last two hours and your pet is not yet showing clinical signs, your vet may induce vomiting to remove the toxic material from the stomach. This may be followed by the administration of activated charcoal, which binds to remaining toxins in the gastrointestinal tract to prevent them from entering the bloodstream.
For pets already showing signs of anemia, supportive care is vital:
Your vet may incorporate specific therapies to help combat oxidative damage and support recovery:
The prognosis for Allium toxicosis depends heavily on the amount ingested, the sensitivity of the individual pet, and how quickly veterinary treatment is initiated.
For mild to moderate cases where only a small amount was consumed, the prognosis is excellent once the source of the toxicity is removed. As noted in a leading veterinary internal medicine reference:
"If only a moderate amount of onions has been eaten, the Heinz body anaemia resolves spontaneously after discontinuing the onions (Kaplan A 1995, Robertson JE et al. 1998)."
In these cases, the pet's bone marrow will naturally produce new, healthy red blood cells to replace the damaged ones over several weeks.
However, for severe cases or when large quantities are consumed, the prognosis is much more guarded. Massive destruction of red blood cells can lead to severe systemic complications:
"In more severe cases, icterus and renal failure can be seen as a consequence of the haemolysis and haemoglobinuria respectively, and possibly death (Cope R 2005, Ogawa E et al. 1986)."
If kidney failure develops, intensive, long-term hospitalization is required, and the risk of mortality increases significantly.
Onion and garlic toxicity is entirely preventable. Because pets are highly sensitive to these ingredients, you should take the following precautions:
If you suspect or know that your pet has eaten onions, garlic, or any food containing them, call your veterinarian or an animal poison control center immediately. Do not wait for clinical signs to appear, as early decontamination can prevent severe anemia.
Seek immediate emergency veterinary care if your pet exhibits any of the following red-flag signs:
Treatment must be prescribed by a licensed veterinarian based on your pet. Specific drug doses are intentionally not shown here.
Onion and garlic ingestion causes oxidative damage to red blood cells in dogs and cats, leading to Heinz body anemia, weakness, and potentially life-threatening kidney damage.
Heinz body anaemia、Eccentrocytes、Haemoglobinuria、Increased serum bilirubin、Lethargy、Pale mucous membranes、Tachycardia、Tachypnoea
Heinz body and eccentrocytes identification、Urinalysis
Treatment must be prescribed by a licensed veterinarian based on your pet. Specific drug doses are intentionally not shown here.
This article is for general education and is not a substitute for professional veterinary advice. If your pet is unwell, please consult a veterinarian.
Peqaboo’s AI helps you track symptoms, understand lab reports, and know when to see a vet.
Get the Peqaboo app