Tea tree oil or grapefruit seed extract work well. Also, be sure to disinfect shoes and socks, also. Wash socks in HOT water.
Go to the doctor and find out the cause. My son's chronic athlete's foot was caused by an overgrowth of yeast in his system. It also causes thrush and some other skin issues. After switching to a mostly organic diet and probiotics, he hasn't had any issues in a few years.