Garlic at high doses may cause anemia (Heinz body anemia) in animals... Look at what I have just found about garlic.
"The main component in raw garlic is alliin. But as soon as you crush or cut a clove of garlic, an enzyme called alliinase is released, converting alliin into allicin..Allicin, which gives garlic its odor, is a strong oxidant, that is, a chemical that creates free radicals, which in excess, can be dangerous. Allicin can cause stomach irritation and, in rare cases, hemolytic anemia, destruction of red blood cells. If placed directly on the skin, allicin can cause blistering. During cooking, allicin produces ajoene, DADS (diallyl disulfide) and other compounds that may help keep blood from clotting.
During aging, alliin and allicin are converted to water-soluble compounds such as S-allyl cysteine and S-allyl mercaptocystine, which have little odor, are stable and survive cooking. These are among the ingredients in "aged garlic extract" supplements and may help combat cancer and protect against heart disease.
Garlic also contains oil-soluble compounds like DAS (diallyl sulfide) and DADS which may have beneficial effects on blood pressure, lipids and clotting and may help prevent cancer."