Today’s ‘herbal healers,’ praise the benefits of Usnea to treat upper respiratory infections, and as a potent anti-bacterial medication. Usnea is a species of hanging hair lichen often known as witch’s hair or old man’s beard.Lichens don’t often pop up in everyday conversation, but that may soon change. Like the canary in a coal mine, lichens – which prefer pristine environments – have become an important tool for scientists who study pollution.