Dogs, and especially cats, are sensitive to garlic, Jaspar. Unfortunately, we do not know specifically what dosage causes problems, and it is not yet completely known what breeds and age groups are most sensitive to this toxicity. What we do know is that gastrointestinal problems and red blood cell damage can occur as a result of feeding garlic to pets. An occasional small amount, such as that in most commercial pet foods and treats, may not cause a problem, but because of the risk, we generally recommend that you avoid feeding your pets products that contain more concentrated amounts of garlic.
For more information, please take a look at our Top 10 People Foods to Avoid Feeding Your Pets.