Those concerned about bare feet always seem to mention athlete’s foot. Here is part of a Question and Answer from Dermatology Insights, Volume 3, Number 1, page 30 (2002). It was published by American Academy of Dermatology. I’ve emphasized some of the text:
Q: Why does athlete’s foot develop?
A: Athlete’s foot is a term used to describe a fungus infection of the feet. The correct term for athlete’s foot is tinea pedis. The fungi that cause athlete’s foot grow in moist, damp places. Sweaty feet, not drying feet well after swimming or bathing, tight shoes and socks, and a warm climate all contribute to the development of athlete’s foot. It’s commonly believed that athlete’s foot is highly contagious — that you can easily catch it from walking barefoot in the locker room. This is not true. Experiments to infect healthy skin with athlete’s foot have failed and often one family member may have it without infecting others living in the same house. It’s not clear why some people develop athlete’s foot and others don’t.
. . .
Q: How can you prevent athlete’s foot?
A: Wash your feet daily, and always dry your feet thoroughly, especially in between your toes. Avoid tight footwear, especially in the summer. Sandals are the best warm weather footwear. You should also use an anti-fungal powder on your feet and in your shoes during the summer. Alternate shoes so that they have a chance to dry out at least 24 hours before re-wearing them. Cotton socks (or socks made of a material that takes moisture away from the skin) are best and you should change them if they become damp. Whenever possible, go barefoot at home. Athlete’s foot does not occur among people who traditionally go barefoot. It’s moisture, sweating and lack of proper ventilation of the feet that present the perfect setting for the fungus of athlete’s foot to grow.
I might add that going barefoot all the time, not just at home, is even better.