No this is not common. Ask your vet to check the dogs eyes carefully for entropian eyelids. Ask for another skin scraping as some mites do not show up first time. If nothing comes of this then go to another vet. The fact that the condition seems to clear in the cold weather would suggest either a parasite problem or, more probably, an allergic reaction to something, possibly a pollen.
Suggest these possibilities to your vet and if you are unhappy with the response you get try another vet.