Thanks for placing your query here.
I can appreciate your concerns.
It seems the boy is having some infection.
the possibilities are bacterial infection (also called pyoderma
) or fungal infection
(also called kerion).
my advice would be to stop all medications & seek a skin specialist's opinion.
Taking a swab for bacterial culture will be useful , as well as a KOH swab for fungal staining.
Cow milk allergy
in not a likely cause.
Hope I have answered your query.
If you have any further questions I will be happy to help.
Wish your baby good health.