Check him very, very carefully to see if he has any patches where the hair has thinned (like bald patches). They are obvious if on the face, but less obvious elsewhere if the hair covers them.
Hans was diagnosed with demodex after he scratched mercilessly. We gave him a few weeks to see if his immune system would get rid of it but in the end had to put him on ivermectin.
Rough Collies - King (01/1994-01/2002) and Samson (2/14/2002-3/30/2014) - too good for this world
GSD - Hans (12/31/2013)