Your dog is having mange infection. Apply Tactik lotion 4 ml mixed in 1 litreof water on his body after bathing once a week. Apply a few drops of tactik mixed in 2 spoons of turpentine oil inside his ears bonce a week.
If it is active and better than yesterday then you can wait and watch. Watch for signs and symptoms of dehydration. Give some simple food which can be easy to digest. Give sufficient fluids. Go to your pet doctor if it does not recover fully.