Usnea is not to be confused with Spanish moss. Infact Spanish moss derives its latin name from Usnea.(Tillandsia usneoides, the ‘Usnea-like Tillandsia’)
The Usnea species, at one time widespread and luxuriant, almost entirely disappeared from a major area of England and Wales covering at least 68 000 km² and at least 6 000 km² of lowland Scotland, mainly as a result of the increase in atmospheric pollution.Usnea is very sensitive to air pollution, especially sulfur dioxide. Under bad conditions they may grow no larger than a few millimetres, if they survive at all. Where the air is unpolluted, they can grow to 10–20 cm long.
An article by M. B. in U.S. Med. Invest. (quoted New, Old, and Forgotten Remedies) gives an observation by the writer, who ate a little of the “moss” and had in consequence a severe congestive headache which compelled him to give up his work and go to bed. He got to sleep and woke very well next morning. Two young ladies out picking cranberries had headache from riding in the hot sun and were compelled to lie down. Usn. b. Ø, one drop in a tumbler of water, a teaspoonful to be taken at once and repeated in fifteen minutes. The second dose stopped the pain. A young married lady subject to headache for five years; was almost frantic with the pain. Usn. b., as above, cured in one or two doses.
Head began to ache; soon could feel the blood press into the brain; with domestic attentions he got to sleep, and woke next morning uncommonly well.─Pain over entire head or front head, with feeling as if temples would burst or eyes burst out of sockets.