Yes it is a bit confusing about garlic, however I hope that I can clarify things for you.

Garlic is safe to give to dogs and other animals if given in normal sensible amounts. In fact we have been adding it to some of our pet food recipes and have sold garlic as a separate product (Denes Garlic Tablets) for over 50 years without any particular issues over its safety. It seems that garlic can only cause problems if given in very large amounts over long periods of time where it can cause abnormalities in the blood. This was demonstrated in some laboratory trials where large amounts were fed to rats over a long period of time resulting in blood changes.

In addition, we monitor suspect reactions to our herbal medicines extremely carefully. Over the last 50 years or so we have had a few reports of our Garlic Tablets causing occasional vomiting, but no issues involving the blood or other health issues arising from feeding garlic. Our conclusion therefore is that garlic is a safe and useful herbal medicine if used properly.