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Usnea barbata is a pale green or gray lichen native to Europe, Asia and the Pacific Northwest of North America. It can be most often found in woodlands where it grows on older trees. Also known as beard lichen, old man’s beard, oak moss or tree moss, it grows in stringy clumps hanging from branches. The lichen is parasitic in nature and can cause significant damage to the host tree.
Like all lichens, usnea barbata is an amalgam of fungus and algae growing together in a symbiotic relationship. The lichen appears to be a single organism unless observed under a microscope, when the algae can be observed living in the body of the fungus. It is the presence of the algae that makes the lichen capable of photosynthesis.
For thousands of years, usnea barbata has been used as a traditional herbal remedy. Ancient Egyptians, Greeks, Chinese and Native Americans relied on this lichen for its medicinal properties. That legacy continues with modern herbalism and alternative medicine.
As a source of usnic acid, usnea barbata is reputed to have antibiotic properties. It has an unpleasant, bitter taste but can be eaten safely, though it is more commonly taken in tablet form or as a tincture. Usnea barbata has been used internally to treat bronchitis, respiratory infections, urinary tract infections, cold and flu symptoms and digestive complaints. There even have been claims of its effectiveness as a cancer treatment, but there is no medical evidence to support its use for any medical condition.
Externally, it has been used to dress wounds, acting as both a pad and an antibiotic. Usnea barbata is also known as an antifungal agent, and it can be used to treat ringworm, athlete’s foot and other fungal infections. The lichen can be applied directly to the skin but is more commonly applied as a cream. It also has been used to produce lozenges and mouthwash.
Usnic acid has also been used as an ingredient in some over-the-counter weight-loss supplements. The United States Food and Drug Administration received 21 reports linking liver toxicity to one supplement in particular, a supplement called LipoKinetix®. This prompted the FDA to issue a warning about the supplement in 2001. Both usnic acid and usnea barbata were nominated for further investigation by the National Toxicology Program. No findings have been reported.