Don't remember what we used but we treated the entire yard & house with an insecticide to get rid of the fleas. Dog was very allergic. Took him to the vet. He got steroids and a tranquilizer which kept him calm (almost knocked out) for a few days. When he was relaxed it didn't bother him as much and when he was calm he started to feel better.
Then we started using one of the monthly ointments on the back of his neck.