In the world the onion has cultivated as consumed vegetable and it has contains different bioactive compounds it has very important for health. The onions are antioxidant, anti-obesity, anti-inflammation, anticancer, antiallergic and anti-diabetic properties. It contains phenolic compounds which have beneficial for the health. The onion has botanically known as Allium cepa the Latin word cepa means onion or bulb. The plant has bluish green leaves and bulb at the base, the bulb has composed shorten compressed underground stem surrounded by fleshy modified scales it envelop central bud at tip of the stem. The onion plant has described firstly by the Carl Linnaeus in his book Species Plantrum in 1753. The onion has contains antioxidant pigment known as quercetin, mostly it contain water which has 89%, including 4% sugar and 2% dietary fiber it contains 9?rbohydrates, 1% protein and also contains some essential nutrients. The onion also contains organosulfer compounds like vinyl dithiins, cepaene, trisulfides and disulfides this compounds has health functional property like anticancer and antimicrobial activities. The quercetin has effective against many disorders like cardiovascular diseases, breast cancer, colon cancer, ovarian cancer, gastric cancer, lung cancer and bladder cancer. The spring onion has known as green onion which has contains essential nutrients and vitamins like vitamin A, C and B12 the minerals like copper, phosphorus, magnesium and potassium. The onion also used for the treating digestion problems like loss of appetite, upset stomach and gallbladder disorders. It also treats heart and blood vessel problems like chest pains and high blood pressure; it also prevents the hardness of arteries. The onion also helpful in treating sore mouth and throat, whooping cough, bronchitis, asthma, dehydration, intestinal gas, diabetes and parasitic worms. It also used as diuretic for increase urine output. The onion directly used on insects bite, wounds, light burn, boils, bruises and warts. It is estimate that that in large populated developing countries has depends on medicinal plants and traditional medicine for the primary health demands meet. The herbal medicine has also given contribution in human well-being over age according to history. The onion also a traditional herb medicine has been used in different health disorder from the ancient times. The plants contains flavonoids, phenols, alkaloids, tannins, terpenes, steroids, saponins, stibenes and glycosides with more phytochemical constituents has responsible for therapeutic effects attributed to medicinal plants.