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Usnea, also known as old man’s beard, is a type of lichen that grows on the trees, bushes, rocks, and soil of temperate and humid climates worldwide (1).

It has long been used in traditional medicine. The ancient Greek physician Hippocrates is believed to have used it to treat urinary ailments, and it’s regarded as a treatment for wounds and inflammation of the mouth and throat in South African folk medicine (2).

Nowadays, usnea is commonly used to aid weight loss, soothe sore throats, accelerate wound healing, and reduce pain and fever. Some people even suggest it may help fight certain types of cancer (1).

This article reviews the scientific evidence to tell you everything you need to know about usnea’s benefits and side effects.

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Usnea’s main compounds and uses

Although lichens like usnea may look like single plants, they consist of an alga and a fungus that grow together.

In this mutually beneficial relationship, the fungus provides structure, mass, and protection from the elements while the alga produces nutrients to sustain them both (1).

Usnic acid and polyphenols, the main active compounds in usnea, are thought to provide most of its purported benefits (3).

Compounds called depsides, depidones, and benzofurans may also have health effects, but more research is needed (1).

Usnea is made into tinctures, teas, and supplements, as well as added to various products like medicinal creams. It’s common to take it orally or apply it directly to your skin.

Usnea is a lichen rich in usnic acid and polyphenols. It’s available as a tincture, tea, supplement, and medicinal cream.

Potential health benefits

Usnea is said to offer a range of health benefits, from weight loss to pain relief to cancer protection. However, few of these uses are supported by current research.

Here are the potential benefits with the most scientific backing.

May promote wound healing

Usnic acid, one of the main active compounds in usnea, may help promote wound healing.

Test-tube studies suggest that this compound may fight infection-causing bacteria, reduce inflammation, and stimulate wound closure (4, 5).

Research in rats shows that usnic acid increases markers of wound healing, such as collagen formation, when applied directly to wounds. The lichen’s anti-inflammatory properties may be responsible (6).

There’s also evidence that usnic acid may protect against Staphylococcus aureus bacteria, which are often responsible for skin infections (7, 8).

However, it’s currently unclear whether the amounts of usnic acid present in certain skin care creams are sufficient to provide these same benefits. Therefore, more human studies are needed.

May protect against certain cancers

Usnea is rich in polyphenols, a type of antioxidant that helps fight cell damage caused by unstable compounds known as free radicals.

In turn, this antioxidant activity may safeguard against various diseases, including cancer (2, 9, 10, 11).

Test-tube studies further suggest that usnic acid may help prevent cancer cell growth and kill cancerous cells while selectively avoiding non-cancerous ones (2, 12, 13, 14).

Although these results are promising, more studies are needed.

May promote weight loss

Usnic acid, the main active compound in usnea, is a popular ingredient in weight loss supplements, including fat burners. It’s believed to promote weight loss by increasing your metabolic rate (15).

Although it may be effective, many reports suggest that oral weight loss supplements containing usnic acid, like LipoKinetix, may cause liver failure and even death (15, 16, 17, 18, 19).

Most people recovered after they stopped taking such supplements. However, a proportion experienced severe liver failure, required an emergency liver transplant, or died (17).

While it isn’t clear whether usnic acid caused all of the ill effects from these multi-ingredient supplements, usnic acid and fat burners containing usnic acid are not recommended to boost weight loss due to the notable safety concerns.

Usnea may promote wound healing, combat cancer cells, and aid weight loss. However, its use is discouraged due to its side effects, and human research is lacking for its wound healing and cancer effects.

Safety and potential side effects

When taken by mouth, usnic acid, the main active compound in usnea, has been linked to several cases of severe liver failure, the need for an emergency liver transplant, and even death (16, 17, 18, 19, 20).

Animal research suggests that diffratic acid, another usnea compound, is toxic to the liver when consumed in large amounts (21).

Moreover, some evidence indicates that drinking undiluted usnea tinctures or large quantities of strong usnea tea may cause stomach upset (1).

Dosages of usnic acid and diffratic acid can vary widely between supplements, and the doses large enough to produce any negative effects aren’t known.

Therefore, further safety studies are needed.

In the meantime, you should employ caution before using usnea teas, tinctures, or capsules. Consider consulting your healthcare provider before adding these products to your routine.

Applying products containing usnea or usnic acid directly to your skin may be a safer alternative, though some people may experience a red, itchy rash (22).

Due to a lack of safety research, children and pregnant and breastfeeding women should avoid usnea.

When taken by mouth, usnea may cause stomach upset and severe liver damage. Children and pregnant or breastfeeding women should completely avoid it, while all others should practice extreme caution.

The bottom line

Usnea is a lichen that has been used for centuries to cure various ailments. While it’s said to offer numerous health benefits, very few are currently supported by science.

Some evidence suggests that usnea may aid wound healing and protect against certain cancers — though further studies are necessary.

Furthermore, while it may boost weight loss, it isn’t recommended for this purpose because of severe side effects.

In fact, when taken by mouth, usnea may cause stomach upset, severe liver damage, and even death. You should practice extreme caution with this supplement and always consult your healthcare provider before taking it.