Onion Poisoning (Allium Toxicosis) in Dogs

Summary

When dogs eat garlic, onions, or other Allium species, red blood cell damage results. This is often called onion toxicosis, no matter what type of allium plant was consumed. Onion toxicosis is potentially life-threatening.

After eating a sufficient quantity of plants from the allium family, dogs develop either or both of two groups of symptoms: GI irritation and anemia. Gastrointestinal irritation such as vomiting, diarrhea, and abdominal pain occur shortly after ingestion. Symptoms of anemia develop over the next several days, which include rapid breathing, lethargy, appetite loss, and pale gums.  The goal of early treatment is to remove all possible ingested material to limit damage to blood cells. There is no antidote for onion toxicosis; severely anemic dogs require oxygen support and blood transfusions.

Risk Factors

Professional advice from a pet poison hotline or veterinary professional is helpful for determining the risks associated with onion ingestion. All forms - fresh, dried, and powdered - are toxic with powders being the most concentrated, garlic being the most toxic (3-5 times more toxic than onions), and chives and leeks the least toxic. The toxic dose of fresh onions in healthy dogs is anything over 15 grams per kilogram of body weight. 

Timely intervention immediately after ingestion makes a big difference in the prognosis and is the best way to avoid serious health effects. Onion toxicosis is potentially lethal if enough is consumed to cause a life-threatening degree of red blood cell damage.

Possible Causes

Onion poisoning results when a dog consumes a toxic dose of garlic, onions, chives, or leeks, either all at once, or after small ingestions over time. Onions and other plants in the allium family contain oxidizing compounds that damage red blood cells. If the dog’s red blood cell regeneration cannot keep up with the damage, anemia results.

Main Symptoms

Dogs who eat onions may experience mild temporary gastrointestinal symptoms such as: 

• Decreased Appetite • Vomiting • Diarrhea • Lethargy • Abdominal pain • Drooling

Symptoms of anemia or red blood cell damage include:

• Weakness • Elevated heart rate • Increased respiratory rate and effort • Panting

• Pale gums • Red urine 

Sometimes onion toxicosis also leads to kidney damage. Symptoms include:

• Increased drinking • Increased or decreased urination • Vomiting • Decreased appetite

Detailed Characterization

While ingestion of any amount of onion (and other Allium species) causes red blood cell damage, healthy dogs have an abundance of red cells and are always making more. The prognosis depends on the amount consumed and the extent of resulting red blood cell damage.

Testing and Diagnosis

Dogs presenting for treatment within four hours of ingestion of a potentially dangerous dose of onion, etc., undergo induction of vomiting or gastric lavage to remove as much onion from the digestive system as possible. Dogs with no known ingestion presenting with symptoms of anemia undergo routine diagnostic testing such as physical examination, bloodwork, and urinalysis.

Steps to Recovery

Dogs presenting for treatment within four hours of ingestion of a potentially dangerous dose of onion, etc., undergo induction of vomiting or gastric lavage to remove as much onion from the digestive system as possible. Dogs with no known ingestion presenting with symptoms of anemia undergo routine diagnostic testing such as physical examination, bloodwork, and urinalysis.

Prevention

To reduce the possibility of onion toxicosis do not allow access to onions, garlic, chives, or leeks. Strategies include

• Cleaning up promptly if these plants are dropped on the floor while cooking; keeping dogs out of the kitchen while preparing food

• Fencing any garden beds containing these plants  

• Ensuring any indoor plants, garlic braids, or other means of growing or storing these plants are well out of reach of pets

• Not sharing people food; storing leftover people food in sealed containers away from pets

Is Onion Poisoning Common in Dogs?

Ingestion of Allium spp. plants is common in dogs, but ingestion of enough to cause life-threatening anemia is not. Eating small portions of foods seasoned with these plants does not usually pose a significant risk to healthy, larger dogs.

Typical Treatment

Induction of vomiting, gastric lavage, activated charcoal, blood cell count, intravenous fluids, supplemental oxygen, blood transfusion