Rhinitis Treatment Care

Hi!
I just adopted a three year old Shih Tzu from a shelter. He is an amazing dog, but the last few days he has been sneezing quite a bit with a clear discharge coming from his nose. The vet said it is probably hay fever. Has anyone else ever had a Shih Tzu with this issue? Any advice to make him as happy and comfortable as possible? He has been sleeping quite a bit – want to make sure that he is feeling 100%. Thanks!