Thanks for the query,
It can be due to moisture.
The other possibility is candida infection.
Please get a KOH mount of the scraped fluid done.
This will help in diagnosing fungal infection
Probably you are suffering from
Please meet a dermatologist
for exact treatment.
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.