Book excerpt: Growing numbers of pet owners are giving their pets dietary supplements in hopes of supporting their health. Many people presume that supplements are safer than drugs, but the reality is that there are very limited safety data on dietary supplements for pets. Many challenges stand in the way of determining whether animal dietary supplements are safe and at what dosage. Supplements considered safe in humans and other species are not always safe in horses, dogs, and cats. An improved adverse event reporting system is badly needed. Also, the absence of laws and regulations that specifically address animal dietary supplements causes considerable confusion to the industry and to the public. Clear and precise regulations are needed to allow only safe dietary supplements on the market. This book examines issues in determining safety of animal dietary supplements in general, and the safety of three animal dietary supplements; lutein, evening primrose oil, and garlic, in particular.