Usnea is used for acute and chronic lung infections, such as pneumonia, and for treating colds and influenza, and as an adjunct to tuberculosis (TB) treatment. Usnea kills bacteria by disrupting their metabolic function through cutting off the energy supply to their cells. Unlike bacterial cells, human cells are less permeable to usnic acid and are not adversely affected. It can be used as a wash for the treatment of impetigo which is a bacterial infection of the skin.
Usnea is also active against several viruses that present sores and lesions including the Epstein-Barr, herpes simplex and polyomavirus (a tumour causing virus) as well as the Junin and Tacaribe viruses.
Usnea has also shown to be effective as an antifungal against Candida albicans.