Kay,
The fastest way to relieve the itchies is a cortisone shot. The vet has to administer it. When Dusty breaks out from his allergies, we give him the antibiotic along with 20MG of cortisone (internal) for a few days (high dose) and then wean him to 5MG every other day for maintenance. After he's been on maintenance for a week, I wean him off.

His allergies are environmental so I have to bath him several times a week in clear water (no soap). Topically, I use an over the counter cortisone cream. Any topical that works for humans to relieve itch will work on the dog too. Hot Humid weather is the worst time of year for Dusty's allergies so we are fighting it right now too.