Why Do I Have An Intermittent Odd Burning Itch On My Feet, Behind The Knee, Abdomen And Back?

I have a odd burning itch that just happens periodically with no apprent cause on the skin on tops or sides of my feet, behind the knee ,abdomen and back. There is no rash or visible signs of cause. It is localized, not over a large area. Scratching it makes it much worse. It will subside after awhile if it is ignored or possibly just rubbed a little. Calamine lotion seems to help a little.