Oregano oil (CAS 8007‑11‑2) is a natural volatile oil extracted from oregano of the Lamiaceae family, and is a feed medicinal additive approved by the Ministry of Agriculture of China. Its main active ingredients are carvacrol (approximately 60%) and thymol (about 8%). It is a pale yellow to brown‑red oily liquid with a pungent odor, insoluble in water but soluble in ethanol and non‑volatile oils, with a boiling point of 236–237 °C and a density of approximately 0.939.
Oregano oil exerts broad‑spectrum antibacterial effects by penetrating the cell membranes of pathogens and disrupting their water balance. Its active components function by damaging pathogenic bacterial cell membranes and inhibiting protein synthesis and DNA replication. It shows remarkable inhibitory effects against livestock and poultry pathogenic bacteria such as Escherichia coli and Salmonella, and can improve meat quality and feed utilization efficiency. Studies have confirmed that carvacrol, its principal active ingredient, also inhibits phytopathogenic fungi including Sclerotium rolfsii. Besides being used as a feed additive, oregano oil can also be applied to egg preservation and pharmaceutical fields. In 2024, the European Food Safety Authority (EFSA) assessed that Spanish oregano oil is safe as a sensory additive for all animal species under recommended conditions of use, and proposed the maximum dosage in compound feeds. In 2026, the European Commission issued a regulation refusing the approval of carvacrol preparations as feed additives for weaned piglets. As a feed additive, its premix form can be used synergistically with other feed ingredients for the prevention and treatment of digestive tract diseases in livestock and poultry.