Thanks for the query,
Probably You have developed an allergic reaction
Location of rash exactly at same place suggests this.
It is called as contact dermatitis
Please change your slipper.
Apply a mild steroid lotion like desonide
Also take an antihistamine tablet.
This will give you some relief.
Please meet a dermatologist
for exact diagnosis.
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.