Thank you for the query.
This area (especially when covered with clothes) has moisture and warm environment. This creates great environment for infection, especially for fungal infection
. It is more possible if you have some redness
or itching in this area as well.
I suggest you to consult dermatologist
with this issue. Some antifungal agent might be necessary. You should also keep this area dry and clean. Lose underwear is a good idea.
Hope this will help.