Whatever the cause, you have a problem, obviously, and if it were me, I would get pure DMSO from Amazon (around $10) and dilute it 1part DMSO to 10 parts water and swab all over feet and let dry then cover with a healing moisturizer (again, a cheap drug store variety will work or you can get a fancy expensive herbal type). Treat once a day at first to make sure you don't have a reaction to the DMSO. Experiment with how much you can tolerate without any irritation. Melaleuca essential oil would be great too but is way more expensive. DMSO is an AMAZING anti-bacterial/anti-fungal. Get a book on it at Amazon and you will be glad you bought the 99.9% pharmaceutical grade as it will last a long time and can be used for so many things. But it will DEFINITELY heal your feet. Then make sure you keep lotion on your feet every night before you go to bed. I used to have terrible issues with fungus and infections on my feet since I was a little girl and now at 53 they are baby soft and not a sore or crack to be seen - ever! Blessings!