I live in North Mississippi and have this same plant you are describing everywhere~  I have thought all this time that it was poison ivy, until I saw pics of the Virginia Creeper.  That looks just like what is growing all over (literally) our place.  But I also have a nasty, blistery rash from the top of my forehead to the tops of my feet.  And everywhere in between...LITERALLY.  From bikinin line too palms of hands and also buttocks!  So am I that allergic to Virginia Creeper?