Unfortunately, this is not possible without affect all unrelated body parts.  BTW, to apply setting changes to all body parts in the Material Room, right click in an open area to bring up the menu, select all, and then apply to all.  As mentioned, this will apply changes to everything and it is not very practical for whole body skin textures.  The only system, at present, which can accomplish a one click settings change, has been developed by Bill Baggins and can be found elsewhere in this forum.  Look for VSS Skin Test.

Edit:  This is the link:

http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2737823