Garlic (Allium sativum) is a relative of onions and is an ancient food and medicinal plant.
Garlic, and onions, are toxic to dogs and cats at certain dosages. One study found that 15 to 30 g/kg can make a dog sick, especially is the dog has anemia.
In smaller amounts, such as those provided in nutritional supplements, garlic used by some naturopathic veterinarians for its immune system stimulating properties.
Garlic is sometimes used to treat parasitic infections. A 2008 study using mice found that garlic is as effective as the antiparasitic medication ivermectin in killing intestinal parasites.