Asking for a friend: orange fluid filled blisters appearing on head and beside ears

[Zoe_boe]

A friend of mine has fluid filled blisters on his head which have bright orange fluid, he has no hair as he has gone bald (not recent), he always wears a hat and he now has some near his ears but no where else on the body. He is awaiting a skin biopsy but I was wondering if anyone has any ideas what it could be? Links to photos:

https://ibb.co/1fT7bjS
https://ibb.co/bmfDqJs
https://ibb.co/MBhRHJJ