Thanks for the query.
you might have developed a fungal infection
This causes itch which then gets infected by bacteria.
You need treatment with both anti fungals as well as oral antibiotics
Keep using ketoconazole
along with that you can also use sebowash shampoo.
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.