Traditionally, the medical properties of garlic were recognized as early as 3000 BC. The functional benefits of garlic are its antimicrobial activity, anticancer activity, antioxidant activity, ability to reduce cardiovascular diseases, improving immune functions, and anti-diabetic activity. Recent studies identify the active functional components providing the medicinal benefits, as well as their mechanisms of action including the best possible ways to consume garlic. Allicin (diallyl-thiosulfinate) is one of the major organosulfur compounds in garlic considered to be biologically active. In this article, I review the chemistry of allicin and its stability during processing and storage, in-vivo and in-vitro functionality of allicin, and other functional components. In addition, I explore other potential alternative approaches of making its derivatives and their use for health benefits.