I have one itchy spot on my neck for a month now--no scabies-no lice- not allergic to any soaps--no new clothing--no scabies--what is it?

Hard to speculate: This may have started off as a simple reaction to something you came in contact with. If it has persisted this long it may be what is labeled a neurodermatitis, a fancy label for changes that occur if you itch & scratch producing more itching & scratching. It may respond to an otc hydrocortisone cream and your willful effort to avoid scratching for a couple months. Your doc may need to see it.