Black seed oil is extracted from Nigella sativa, commonly called black seed, explains Cathy Wong for About.com. A mainstay in alternative medicine, black seed oil contains thymoquinone, a compound with antioxidant qualities. Throughout history, black seed has been used to treat allergies, asthma, flu, headaches and rheumatoid arthritis.
While research on the effects of black seed oil is limited, the oil is thought to ease inflammation and boost the immune system, according to Wong. Black seed oil is edible, as it is derived from a culinary spice and can also be used for cooking. Black seed oil is found at health food stores.