Elderberry, or elder, has been used for centuries to treat wounds, when applied to the skin. It is also taken by mouth to treat respiratory illnesses such as cold and flu. In many countries, including Germany, elder flower is used to treat colds and flu. Some evidence suggests that chemicals in elder flower and berries may help reduce swelling in mucous membranes, such as the sinuses, and help relieve nasal congestion. Elder may have antiinflammatory, antiviral, and anticancer properties.