Are Purple Discoloration And Swelling In The Face Serious Concerns?

Hello, dear doctor, My friend has had a swollen face around the cheekbones for circa 9 months now with a purpleish coloring. Both sides are affected, but the swelling sometimes alternates with on side more swollen than the other. He went to a dentist for consultation, but nothing was found to indicate any problem there. What could be the cause? Thanks.