Usnea

• Usnea species are classified as fruticose lichens, which are a symbiosis of fungus and algae. Usnea grows on the bark and wood of coniferous (e.g., spruces, firs, and pines) and deciduous hardwood (e.g., oak, hickory, walnut, apple, and other fruit trees) host trees throughout the northern hemisphere in Asia, Europe, and North America.
• Usnea has been used as a therapeutic agent in traditional Chinese medicine (TCM) for thousands of years. Usnea longissima is traditionally taken by mouth for lung and upper respiratory infections, and applied on the skin to treat surface infections or external ulcers. It is still used today in TCM in liquid extract and tincture form to treat tuberculosis lymphadenitis.
• Usnic acid is a secondary metabolite uniquely found in all lichens. Usnea or usnic acid has been used as a human papillomavirus (HPV) treatment and as an oral hygiene agent, with limited effectiveness.
• Usnic acid is also found in various oral (by mouth) dietary supplements, including Lipokinetix®, marketed as a weight loss agent. However, Lipokinetix® may not be safe and may cause liver damage. Lipokinetix®, now withdrawn from the market, contained phenylpropanolamine (PPA), caffeine, yohimbine hydrochloride, diiodothyronine and usnic acid.