The only one I can think of, off the top of my head is a fungal TOENAIL infection, as long as you work in a sanitary manner and throw away file/s after use you can give a treatment, as with a FINGERNAIL fungal infection you cannot reason for this being the toes are mostly kept in shoes which are warm moist and dark the perfect breeding ground for this where as fingenails do not. hope this was what you were looking for xx