Usnea (old man's beard) (Usnea barbata): Uses, Evidence and Safety

Safety first: usnic acid and serious liver injury

Usnea is a lichen, not a plant, and it contains usnic acid. Usnic acid in weight-loss supplements has been linked to severe liver injury, including liver failure, liver transplants and at least one death. [1][2][3] The best-known cases involved two products, LipoKinetix and UCP-1, sold in the US until 2001. [3] A review by FDA scientists says the FDA had received at least 21 adverse event reports tied to usnic acid supplements, including one death, and warned consumers about LipoKinetix in November 2001. [2][3] Those products contained usnic acid itself, often with other ingredients, so the cause in each case is hard to separate. [2] Memorial Sloan Kettering states that usnic acid supplements are linked to liver damage, especially at high doses, and that evidence for weight loss is lacking. [1] This page is information, not a recommendation to use usnea. We give no preparation instructions and no amounts. If you already take a product containing usnea or usnic acid and notice yellow skin or eyes, dark urine, belly pain or unusual tiredness, contact a doctor. See also herbs and liver injury.

Overview

Usnea barbata (L.) Weber ex F.H.Wigg. is a lichen (a partnership of a fungus and an alga) in the family Parmeliaceae; GBIF lists it as the accepted name. [4] It is often called old man's beard because it hangs in grey-green threads from trees. Native range: not found in the sources we read for this species as a whole. The FDA-authored review says U. barbata is not native to North America, and that "usnea" sold in the US may in fact be other Usnea species, several of which also contain usnic acid. [2] Reviews report that Usnea species contain roughly 1 to 3 percent usnic acid by dry weight. [2] This page covers usnea lichen and usnic acid products; it is not about similar-sounding mosses or "tree moss" products, which we did not review.

Traditional use (not proof of benefit)

The FDA-authored review notes that dried Usnea lichen is used in Traditional Chinese Medicine. [2] The same review lists small, older Chinese clinical studies of usnic acid for tuberculosis and bronchitis, which reported side effects such as stomach pain, raised liver enzymes, dry mouth, dizziness and nausea. [2] Long use in tradition is not proof that a product works or is safe.

What research shows

Reviews found no controlled human trials of usnea or usnic acid for weight loss. The human information we read is mostly case reports and small older studies. [3][2]

Proper evidence not found in the sources we read for usnea lichen itself (as opposed to isolated usnic acid) improving any health condition in people.

Forms and why the form matters

Usnea is sold as dried lichen, capsules, tinctures (alcohol extracts), teas and topical products. Usnic acid is also sold alone and is used in some cosmetics and oral-care products. [1] Products named "usnea" can be a mix of species, and usnic acid content varies. [2] In animal studies, usnea preparations were more toxic than pure usnic acid at an equal usnic acid content, so a lichen is not "safer" than the isolated compound. [2] MSK also notes usnic acid has been found in kombucha tea. [1]

Safety in more detail

• Liver: acute hepatitis and liver failure in people using usnic acid weight-loss products; onset in some cases within weeks. [1][3] Case reports include a 28-year-old woman taking pure usnic acid who needed a transplant, and a man taking a product with a small amount of usnic acid who also needed a transplant. [3] Laboratory work suggests usnic acid disrupts how liver cells make energy (mitochondria) and creates oxidative stress. [1][2]
• Medicines: MSK says theoretical additive effects with blood thinners (anticoagulants) and animal findings that usnic acid may speed CYP3A4, an enzyme that processes many medicines; the clinical importance is not known. [1] Two case reports describe sharply raised liver tests and a prolonged clotting time. [1]
• Pregnancy: one rat study described poor weight gain, more pregnancy loss and fetal abnormalities at high doses; the review calls the data controversial and gives no human pregnancy data. [3] Avoiding use is the cautious reading; ask a doctor. See pregnancy and breastfeeding.
• Breastfeeding: Proper evidence not found in the sources we read.
• Children: Proper evidence not found in the sources we read.
• Liver and kidney: liver as above. Kidney: not found in the sources we read. We could not read NIH LiverTox (the site blocked automated access).
• Allergy and skin: MSK says topical use may cause local irritation and allergic reactions. [1]
• Genetic damage: results are mixed; a 2022 review calls the molecule not genotoxic but says mutagenicity data are controversial. [3]
• Surgery: no agency statement on usnea before surgery was found; given liver and clotting concerns, tell the surgical team about any product. See supplements before surgery.
• Quality: products may be other Usnea species and may be mixed with other ingredients; LipoKinetix also contained stimulant ingredients, which makes blame hard to assign. [2] See adulteration and mislabeling.

Official statements

• FDA (US), November 2001: warned consumers about LipoKinetix after reports of liver injury and recommended the manufacturer withdraw it, as described in two reviews (we did not read the FDA notice itself). [2][3]
• FDA nomination to the National Toxicology Program, 2005: usnic acid was nominated for toxicity evaluation, per the 2008 review. [2]
• Memorial Sloan Kettering, page last updated February 2021: supplements linked to liver damage; weight-loss benefit not supported. [1]

Related pages

• Herbs and liver injury
• Herbs for weight loss: claims checked
• Herbs for immune support: claims checked
• Ephedra and other banned herbal ingredients
• Hidden drugs in supplements
• How supplements are regulated