Background: Allicin is an organosulfur and defensive compound found in garlic (Allium sativum L.) and other Allium species. Its unique odor is easily detectable, and its effects on human health have been studied since ancient times. Scope and approach: In this compressive review we report the presence of allicin in different Allium species, their biosynthesis, pharmacokinetics, absorption, and safety profile. Among the main allicin applications highlight its antimicrobial and antiparasitic properties, reviewed in the present work from in vitro evidence and in vivo studies. Finally, special attention was also given to the allicin state of the art in human health, including in vitro and in vivo assays, and clinical trials, on antioxidant, anticancer, antidiabetic and immunomodulatory effects, besides to its contribution as a cardioprotective agent. Key findings and conclusions: The promising capacity of allicin to interact with thiol groups seems to be directly related to its antimicrobial potential, showing both antibacterial and antifungal activities. Allicin also displayed an interesting potential in the prevention and treatment of several diseases including diabetes mellitus, cardiovascular disease, and cancer. Indeed, its antioxidant and immunomodulatory effects are some of the mechanisms that may explain their biological activities. Future applications should be directed to allicin pharmaceutical formulation, its delivery and its compatibility with food matrices and other drugs due to allicin biosynthesis, instability, reactivity, and volatility.