Black seed (Nigella sativa) is a flowering plant native to Asia and the Mediterranean. Its seed has been used to make medicine for thousands of years.
Black seed might have effects in the body that help boost the immune system, fight cancer, prevent pregnancy, reduce swelling, and lessen allergic reactions by acting as an antihistamine.
People commonly use black seed for asthma, hay fever, diabetes, high blood pressure, eczema, weight loss, menstrual cramps, and many other conditions, but there is no good scientific evidence to support many of these uses. There is also no good evidence to support using black seed for COVID-19.