My dog is 8 and in the last year he has suddenly become extermley itchy along the ridge of his back, 1st he gets sensitive around his back, then gets eruptions along his back, nothing comes out of the eruptions but its very uncomfortable from him. The condition is not seasonal, occurs throughout the year.

Been to the vets and tried numerous things such as:
Prednisone (this helped but cannot be used for a long term)
Anti-itch/ soothing shampoo's
Changed feeds
Already de-flead and wormed

Currently trying anti-histanmines but dont seem to be working at all, vets arnt 100% what it is, bite allergies have been suggested but cant help but thinking is it was bite allergies, wouldnt they be all over not just along his back.

Any ides? Thanks for taking the time to read