Hot, humid weather. Genetic factors, such as fair, sensitive skin. Your own observation of symptoms. Doctor's treatment, if home care fails.
Recurrence is common.
Apply lubricating ointment or cream to skin 6 or 7 times a day. Use cool-water soaks to relieve itching and hasten healing. Pat skin dry, and dust with cornstarch after and between soaks. Expose the affected skin to air as much as possible. Don't use binding materials, such as adhesive tape, or wear tight clothing.