Oregano is a common species of Origanum, a genus of the mint family. It is native to warm-temperate western and southwestern Eurasia and the Mediterranean region. It is a perennial herb, growing from 20-80 cm tall. The plant's flowers are purple, produced in erect spikes. It is sometimes called wild marjoram, and its close relative.
Many subspecies and strains of oregano have been developed by humans over centuries for their unique flavors or other characteristics. Tastes range from spicy or astringent to more complicated and sweet. Simple oregano sold in garden stores as Origanum vulgare may have a bland taste and larger, less dense leaves, and is not considered the best for culinary uses, with a taste less remarkable and pungent. It can pollinate other more sophisticated strains, but the offspring are rarely better in quality. The related species, and Origanum onites (Greece, Turkey). syriacum (West Asia), have similar flavors. A closely related plant is marjoram from Turkey, which, however, differs significantly in taste, because phenolic compounds are missing from its essential oil. Some varieties show a flavor intermediate between oregano and marjoram.
Oregano is an important culinary herb, used for the flavour of its leaves, which can be more flavourful when dried than fresh. It has an aromatic, warm and slightly bitter taste, which can vary in intensity. Good quality oregano may be strong enough almost to numb the tongue, but the cultivars adapted to colder climates often have a lesser flavor. Factors such as climate, seasons and soil composition may affect the aromatic oils present, and this effect may be greater than the differences between the various species of plants. Among the chemical compounds contributing to the flavour are carvacrol, thymol, limonene, pinene, ocimene, and caryophyllene.
Oregano's most prominent modern use is as the staple herb of Italian-American cuisine. Its popularity in the US began when soldiers returning from World War II brought back with them a taste for the "pizza herb", which had probably been eaten in southern Italy for centuries. There, it is most frequently used with roasted, fried or grilled vegetables, meat and fish. Unlike most Italian herbs, oregano combines well with spicy foods, which are popular in southern Italy. It is less commonly used in the north of the country, as marjoram generally is preferred.
The herb is also widely used in Turkish, Palestinian, Lebanese, Egyptian, Syrian, Greek, Portuguese, Italian, Spanish, Philippine and Latin American cuisines. In Turkish cuisine, oregano is mostly used for flavoring meat, especially for mutton and lamb. In barbecue and kebab restaurants, it can be usually found on table, together with paprika, salt and pepper. The dried and ground leaves are most often used in Greece to add flavor to Greek salad, and is usually added to the lemon-olive oil sauce that accompanies many fish or meat barbecues and some casseroles.
Oregano is also used by chefs in the southern Philippines to eliminate the odor of carabao or water buffalo when boiling it, while simultaneously imparting flavor.
Hippocrates used oregano as an antiseptic, as well as a cure for stomach and respiratory ailments. A Cretan oregano is still used today in Greece as a palliative for sore throat. Oregano is high in antioxidant activity, due to a high content of phenolic acids and flavonoids. In test-tube studies, it also has shown antimicrobial activity against strains of the food-borne pathogen Listeria monocytogenes. In the traditional Austrian medicine Origanum vulgare herb has been used internally (as tea) or externally (as ointment) for treatment of disorders of the gastrointestinal tract, respiratory tract, and nervous system. In 2005, the US Federal Trade Commission brought legal action against a firm that had claimed oil of oregano treated colds and flus, and that oil of oregano taken orally treated and relieved bacterial and viral infections and their symptoms, saying the representations were false or were not substantiated at the time the representations were made, and that they were therefore a deceptive practice and false advertisements. The final stipulation on the matter said no representation as to any health benefit could be made without "...competent and reliable scientific evidence...".