Garlic is related to Onions, and Onions have the effect of causing lysis of red blood cells creating anemia. Garlic isn't quite as toxic as Onions, but in some sensitive dogs it can cause problems.

Unless you note your dog breathing excessively fast- give it the better part of your steak tonight and don't worry.

P.S. There is a holistic type of remedy for fleas involving garlic powder. But I sure wouldn't want to give my dogs garlic on a daily basis due to possible side affects.