Looking at the unilateral involvement of foot, it may be dermatophytosis
Dermatophytosis is a superficial fungal infection
Since it is occurring again and again, you should go for blood sugar status. Also try to avoid wetting your feet.
Visit a dermatologist
to know whether it has involved only skin or the nails too. In case nails have been involved, the treatment will be of longer duration.
Dr. Ajit Singh
MD - Skin & VD