If your worried, after you remove as much surface stuff as you can, you can lather your strop up and then take a pumice stone and scrub the surface evenly. After this, take a damp towel and wipe the strop thoroughly all the time rinsing out the towel between wipings. continue until your satisfied its clean. Now allow your strop to dry thoroughly but not in direct sunlight( I pat mine dry with dry rags and then wrap it in a dry towel or hang it over the shower stall until its dry) then apply whatever dressing or leather conditioner you prefer and apply it in your usual fashion.