4-yr old pug got skin disease, fast spreading in 4 months now. Brought to 2 Vets, could not exactly tell what.?

4-yr old pug got skin disease, fast spreading in 4 months now. Brought to 2 Vets, could not exactly tell what. It may be a manifestation of an allergy, that was all the vet could say. I am so worried and helpless.