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 Lipokinetix®, now withdrawn from the market, contained phenylpropanolamine (PPA), caffeine, yohimbine hydrochloride, diiodothyronine and usnic acid.
Ab-Solution plus®, ascorbic acid, atranorin, barbatic acid, binan, depsides, depsidones, diffractaic acid, dihydrousnic acid, evernic acid, glutinol, isoanhydromethyldihydrousnic acid, isodihydrousnic acid, isolichenin, isomethoxide, lichen, Lipokinetix®, longissiminone A, longissiminone B, methylusnic acid, oak moss extract, old man's beard, parmeliaceae, raffinose, sodium usnate, sodium usnic acid, tree's dandruff, tree moss, woman's long hair, Usnea amblyoclada, Usnea barbata, Usnea complanta, Usnea dasypoga, Usnea diffracta, Usnea fasciata, Usnea florida, Usnea ghattensis, Usnea hirta, Usnea longissima, Usnea rubiginea, Usnea siamensis, Usnea subfloridana, Usneaceae (family), usnic acid, usno, Zeta-N®.
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
Usnea and usnic acid both are reported in laboratory studies to have antiviral activity. A combination of usnic acid and zinc sulfate may help treat human papillomavirus. Additional study of usnea alone, and not in combination, is needed to a make a strong recommendation.
Usnea has been used historically as an oral antibacterial agent, and animal and laboratory studies support this. However, there is currently insufficient available evidence to recommend for or against the use of mouthwashes or rinses containing usnea extracts or usnic acid for oral hygiene.