Alum works to treat athlete's foot. Use cooking alum. My Vietnamese wife prepared this treatment for me. Warm up a pot of hot water and dissolve the alum in it. She might have added salt also. Soak the feet in it for an hour. However, I have found apple cider vinegar to be just as effective. Soak the feet in 100% ACV for an hour. Repeat daily for a week or so. Improvement will come after the first or second soak. Keep the feet dry and allow the feet to breathe. Avoid synthetic fabrics. Use only 100% cotton socks and 100% cotton bed linens.