The fruit is used for medicine. Forsythia is used for swelling of small air passages in the lung (bronchiolitis), tonsillitis, sore throat, fever, vomiting, heart disease, HIV /AIDS, gonorrhea, pain and swelling (inflammation), and a severe skin rash with fever and vomiting caused by a bacterium (erysipelas).he fruit is used for medicine. Forsythia is used for swelling of small air passages in the lung (bronchiolitis), tonsillitis, sore throat, fever, vomiting, heart disease, HIV /AIDS, gonorrhea, pain and swelling (inflammation), and a severe skin rash with fever and vomiting caused by a bacterium (erysipelas).