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.

This herbal remedy comes not from a single plant, but from lichen, which is a combination of fungus and alga. Found around the world, usnea hangs from trees like tangled strands of thick hair, earning ...