I cannot diagnose - however, I can tell you, from personal experience, if you live in a humid climate this is not uncommon. When you refer to athlete's foot (crusty), it reminds me of when my children were young and we lived in the southern U.S. It is extremely humid and many times if they had any type of chaffing at all, it would turn into impetigo, which is a fungal infection. Black walnut hull tincture is known for it's anti-fungal properties.