Elderberry (Sambucus nigra) is the dark purple berry from the European elder tree. It has a long history of use for cold and flu. Elderberry is a popular ingredient in supplements. It might affect the immune system, and also seems to have activity against viruses, including the flu. Elderberry is commonly used for the common cold, flu, high cholesterol, and many other conditions, but there is no good scientific evidence to support most of these uses. There is also no good evidence to support using elderberry for COVID-19. Don't confuse elderberry with American Elder, Elderflower, or Dwarf Elder. These aren't the same and have different effects.