Is garlic good for dogs?

Garlic is actually toxic to dogs. Garlic and related plants, such as onions, contain sulfur compounds that attack red blood cells. The loss of oxygen-carrying red blood cells results in an illness called Heinz body anemia, which can be fatal.

Of the various plants that contain these dangerous sulfur compounds, garlic is considered the most potent, especially if the plant is further concentrated into a powder. The toxic principle is relatively slow-acting and does not cause immediate distress. Dogs that eat sufficient amounts of garlic to make themselves sick do not show signs until three to five days later. Symptoms of hemolytic anemia include weakness, refusal to eat, fatigue and dark urine.