Allicin is a sulphur-containing bioactive compound naturally synthesised in several Allium species, including white garlic (Allium sativum L.), bear garlic (Allium ursinum L.) and field garlic (Allium vineale L.). Current literature indicates that allicin exhibits a wide range of therapeutic activities, most notably antimicrobial, antiparasitic, antioxidant, antiviral and antifungal effects. Its biological action is primarily driven by two key mechanisms: rapid penetration into pathogenic cells and the induction of lethal intracellular alterations. The breadth of allicin’s biological properties has prompted growing interest in its potential applications in the livestock industry. Dietary supplementation with allicin has been associated with improved growth performance, enhanced immune function, better quality of animal-derived products and favourable modulation of the intestinal microbiota – an aspect of particular relevance because of the central role of gut microorganisms in animal health. The aim of this review is to summarise current knowledge on the biological properties of allicin, and to particularly consider its effects on intestinal microbial modulation and its potential to improve the production efficiency of livestock