my dog scraps(?) his skin all the time

Now I post here my question, in hope of an answer, because nobody here in Germany can help me.

My dog scraps (<--right word) his skin all the time.
We went to the vet, check everything thats possible, from this little Animals on the skin (I dont know the name), to blood till the dog`s eating.
Nothing helped till this time.

My vet means, that it is possible that there are treatments in our nearest neighboorhood, but we live on the land, not so many people live there.