Im 43 and have had this same condition all my life, cant believe ive waited so long to investigate it and im glad i did now.
After strenuous exercise my face is red down the left side and it is really embarrassing, i hate it , especially when people stare. I try not to let it bother me but when i was a teenager i couldnt cope and gave up on sport altogether.
My left pupil is also larger than my right but have never considered there was a connection to the half face thing. Both eyes are the same colours though.
Think i will investigate a bit further with the GP so that it is recorded in my notes. No-one seems to have mentioned any treatment or remedies do far so i assume we have this for keeps.