Walmart used to carry a hot spot treatment,(sulfa) but they don't have it anymore...and I forgot about the farm store..
On a side note, Hartz flea shampoo had to change their label because it once included it also got rid of lice. People who didn’t want to be seen buying Rid shampoo would buy the dog shampoo and, ya know, we can’t have that.
I hope with all my heart that it helps your poor pup.