There are mixed opinions about giving dogs garlic, though the general consensus is that it is acceptable to do so in moderate amounts. Garlic can actually be used as a repellent for fleas and it can be quite effective for many of them. This particular food also contains a lot of things that help to boost the immune system and fight infection. It has also been proven that regular garlic consumption can enhance liver function, though this is not always true for dogs.
If given in excess, liver can actually damage the red blood cells in dogs which is exactly why you will want to limit the amount you give them. While it is acceptable to give your dog a moderate amount of garlic, you will find that a lot of it might actually harm them.