Is Garlic Toxic to Dogs?

The belief that garlic is deadly toxic to dogs is widespread. However, recent studies suggest that this concern may be overstated, particularly when considering the form and dosage of garlic consumed. And many companion animal nutritionists will agree.

Garlic has been used in the equine industry for years with horse owners swearing by its benefits. But a horse is not a dog so should be treated as so.

Garlic belongs to the Allium family. Same family of vegetables as onion, leek, chive, and shallot. All of these contain a variety of sulfur-based compounds, but only onion, leek, chive, and shallot possess a lot of the worrying compound thiosulfate. This compound is toxic for canines (but not for humans).

When ingested in a large amount in canines, this thiosulfate causes oxidative damage in red blood cells, resulting in “Heinz Bodies” that the body rejects and expels from the bloodstream. Over time this can result in Hemolytic Anemia and may even cause death, but rare.

Examining the Evidence

A pivotal study conducted in 2000 at Hokkaido University investigated the effects of garlic on canine health. 8 Dogs were given 1.25 ml of garlic extract per kilogram of body weight for seven days. As an example, if they used 20kg dogs, each dog woud have been given 100g of garlic (20 cloves of garlic)! The results showed a decrease in red blood cell count and the presence of Heinz bodies, indicators of oxidative damage. However, none of the dogs developed hemolytic anemia or showed outward signs of toxicity. Due to so many flaws in this study, it is easily seen why it cannot be trusted in giving advice on canine nutrition!

In contrast, a 2018 study examined the safety of aged garlic extract (AGE) in dogs. Beagles were administered AGE at doses of 45 or 90 mg per kilogram of body weight daily for 12 weeks. The study found no adverse effects on clinical signs, blood parameters, or the presence of Heinz bodies and eccentrocytes. Additionally, AGE appeared to upregulate antioxidant enzyme genes, suggesting potential health benefits.

''Safe'' Usage Guidelines

The discrepancy between these studies highlights the importance of garlic's form and dosage. Fresh garlic contains compounds that can be harmful in large amounts, while aged garlic extract lacks these harmful compounds and may offer health benefits. However... this does not mean that you should grab what's in your kitchen and start feeding this to your pet. This is for if your pet accidently ingests a bit of garlic or a food that contains garlic. You can buy garlic tablets for pets that have been approved for pet use. However you MUST consult with a vet or a certified nutritionist to establish what is right for your pet.

In conclusion...

While very high doses of fresh garlic can cause oxidative damage to red blood cells in dogs, leading to conditions like hemolytic anemia, small amounts, are not at critically life treatening as once believed. If your pet ingests garlic and you are worried, do not hesitate to ring your vet or the animal poisonline for advice.