Athlete’s foot is the most common fungus that troubles humans, although ringworms come in a close second. Look for a medication whose active ingredient is tolnaftate or clioquinol.
Tolnalfate is particularly effective against athlete’s foot. Remember that skin preparations may themselves cause irritation. If there is no obvious improvement in a week, see your doctor. You should also keep your feet clean and dry, avoid sharing towels, and change your socks regularly to keep athlete’s foot under control.