This could be mositure related. The area needs to be kept clean and dry. Washing with water each time is not good for the skin. The skin needs its natural oils and if you wash them away it will get sore
A cream like Calmospetine is good, but not as good as clean and dry because cream can trap bacteria and moisutre close to the skin and cause an infection too. I only use cream when im really sore or itchy.
If you have hair there, you could shave it (hair traps moisture and dirt too), if you already have shaved it ,it could be ingrown hairs or blocked pores. (its probally best to trim hair rather than actaully shave it).
In short you need to really look after that patch of skin.. keep contact to a minimum, keep it dry and clean, try to blot rather than wipe (wipe irritates the skin, opens the pores and just spreads the bacteria around).
Hope that helps