You may actually have a foot fungus, esp if the callouses are leaving yellow marks behind. MAYBE over-the-counter meds will work for you, but you may want to see a dermatologist, podiatrist, or both to make sure there's no underlying medical reason that would only get masked with the 0-T-C meds. They may have to prescribe something for you. After your morning showers, be sure your feet are dry before putting on your socks, even if you have to blow-dry them. Meanwhile, the best foot powder is one by Dr. Scholl's that comes in a yellow container with a curved neck and a flat green cap. Your feet will remain dry and odor-free all day. You'll want to change your socks every single day...no re-using them the next day. That way your feet can start healing and you won't keep reactivating the sweat that already in them.