Usnea Drug Interactions, Uses, Effectiveness, Safety & More

Usnea is not a plant but a lichen — a combination of a fungus and an alga living together. It often hangs in pale, grayish-green strands from tree bark and is sometimes called "old man's beard." Several Usnea species grow in forests around the world, especially in clean, unpolluted air.

People have used Usnea in traditional medicine for centuries. It is most commonly taken as a tincture or tea, used in throat sprays and lozenges, or applied to the skin in salves. Its long history of use is mainly tied to its reputation as a natural germ fighter.

The most studied active compound in Usnea is usnic acid. In laboratory research, usnic acid appears to interfere with the way certain bacteria and fungi make energy and reproduce, which may explain its antimicrobial reputation. Other compounds in the lichen may add antioxidant or anti-inflammatory effects.

It is important to remember that most of this evidence comes from test-tube and animal studies. How well these effects translate to people taking Usnea by mouth or applying it to the skin is not well established.

The biggest safety concern with Usnea is the risk of liver injury. Concentrated usnic acid, especially in some weight-loss products, has been linked to reports of serious and even life-threatening liver damage. For this reason, oral use of high-dose usnic acid products should be avoided.

People with liver disease, those who drink alcohol heavily, or anyone taking medications that can affect the liver should be especially cautious and talk to a doctor or pharmacist first. Pregnant and breastfeeding women should avoid Usnea because its safety has not been established. It is also not recommended for infants or young children.

Because Usnea is a lichen that absorbs substances from its environment, wild-harvested products may contain pollutants. Choose products from reputable manufacturers.

When applied to the skin, Usnea may occasionally cause irritation or allergic reactions. Some people are sensitive to lichens and may develop a rash on contact.

Taken by mouth, the most serious concern is liver toxicity, which can cause symptoms such as fatigue, nausea, abdominal pain, dark urine, or yellowing of the skin or eyes. If any of these occur, stop use and seek medical care right away. Mild digestive upset is also possible.

There is no well-established standardized dose for Usnea. Products vary widely in strength and in how much usnic acid they contain, which makes safe dosing hard to define.

If you choose to use Usnea, follow the directions on the product label and do not exceed them. Given the liver safety concerns with oral usnic acid, it is wise to check with a pharmacist or doctor before taking Usnea internally, and to avoid long-term or high-dose use.