I have wondered if there is any difference between white & dark eggplant myself. For all I know the people who mentioend it on the net used white but dark was at the grocery store and it worked for me.
Just to be on the safe side - but that's me - I'd rub that area with eggplant for a month or so once a day. Also they say to look for other such things because sometimes when there is one there is another.