Herb library · Herb · Usnea species (Usnea barbata and others)
Usnea
A lichen found worldwide, used in folk medicine on wounds and for sore throats. Its main compound, usnic acid, was sold in weight-loss supplements and has caused severe liver injury, including liver failure.
Serious warning
Taken by mouth, usnic acid (the main compound in usnea) has caused severe liver injury. LiverTox rates it a highly likely cause of liver injury, with cases of liver failure, emergency liver transplant and death, and the FDA issued a warning letter in 2001 over one usnic acid supplement, LipoKinetix.
Traditional use
Usnea lichens grow on trees worldwide. LiverTox notes that lichen extracts containing usnic acid were used in folk medicine on the skin for wounds and athlete's foot, and by mouth for sore throat, toothache and fever. Culpeper's herbal lists it as a moss. Today usnic acid is used in cosmetics, deodorants, toothpaste and medicinal creams, and it was sold in weight-loss and body-building supplements; after reports of liver injury, the FDA issued a warning letter in 2001 about one of them, LipoKinetix, which was withdrawn from the market.
Traditional energetics
Galenic (hot or cold, dry or moist)
Cold. Culpeper's Complete Herbal (1814), p. 241 (opens in a new tab)
What studies show
- Insufficient
Sore throat, wounds and infections: usnic acid acts against bacteria, fungi and viruses in lab studies, but no studies of usnea in people were found for any of these uses.
- Insufficient
Weight loss: LiverTox says the approach behind usnic acid weight-loss products is potentially dangerous and has not been shown to cause weight loss other than through extreme toxicity.
Be careful of
Cautions
- ConditionIn reported cases, liver injury appeared 2 to 12 weeks after starting, with tiredness and nausea followed by yellowing of the skin or eyes. Stop and get medical care right away if these appear.
- AmountLiver failure has followed both pure usnic acid and multi-ingredient products that contained it. LiverTox calls usnic acid a direct liver toxin when taken by mouth in high doses.
- Ask a clinicianTalk with a clinician or pharmacist before using this if you take prescription medicines, are pregnant or breastfeeding, or are giving it to a child.
From the old books
What herbals and dispensaries of the past printed. History, in their words.
“Muscus. Mosse. Is something cold and binding, yet usually retains a smatch of the property of the tree it grows on; therefore that which grows upon oaks is very dry and binding.”
Sources
- Usnic Acid (LiverTox) (opens in a new tab) · NIH · read September 25, 2026
- Hepatotoxicity of usnic acid and underlying mechanisms (opens in a new tab) · NIH · read September 25, 2026
- Fulminant liver failure due to usnic acid for weight loss (opens in a new tab) · NIH · read September 25, 2026
Reviewed September 25, 2026.