Do not use on any part of the body because of sensitizing potential. Oakmoss Concrete is prepared by hydrocarbon solvent extraction of the lichen, Evernia Prunastri, collected mainly from oaktrees in Yugoslavia, France, Italy, Corsica, Morocco, Hungary and various central European countries. The lichen is often soaked in lukewarm water 24 hours prior to extraction. This operation is not absolutely necessary, but it does facilitate the extraction.