SO scared and confused on what to do?

I have a 5 year old lhasa apso who for the past two years has had skin problems, she scratches all the time, now she scratches that much she bleeds we have been doing tons of tests, and they still have no idea whats wrong, they want to send her to a dirmatlogist but it is very very expensive and if its allergies she will be on shots the rest of her life and they said will never get a hundred percent better. She doesnt have much hair bc of it and skin is black ske i know she feels horrible and looks and she is just suffering, family is saying i should put her down so she isnt in pain or suffering anymore, what should i do?