Stiles can't look in the mirror. Can't stand to see his reflection.
It's been a while since seeing his face caused anything other than a sick feeling in his stomach and a powerful urge to break things.
It started when he was eight and his father told him he had his mother's eyes. And the cashier said he had his mother's nose. And some creep from two blocks over said he had his mothers lips.
It got worse when he was nine and his mother started deteriorating and couldn't remember who he was (Sweetheart, what are you doing in here? Have you lost your parents?).
The first time it happened he ended up breaking a mirror and slicing his hand open.
Then he ended up killing her and, well, no amount of therapy will help with that (You have my eyes kiddo. You know what you should do for me? See that knob? Crank it up a few notches. There you go. Thanks sweetheart (It wasn't your fault son, she was sick and she was tired and she manipulated you in -into doing. She tricked you, and it was not your fault Anzelm, never your fault.)).
So Stiles has a thing where he can't stand to see his own face. He decided to call it a phobia years ago. He covered all the mirrors in the house and they don't have anything in the house that can show a reflection.
After Werewolves it doesn't get much better. It actually gets worse. Lydia pulls out a mirror and Stiles flinches so hard he bites his tongue. Allison teaches him Hunting Shit and Stiles paints all of the knives gifted to him black.
People other than Scott, Melissa, and his father start noticing.
No one says anything about it, but the five foot mirror in the entry way of Lydia's house disappears and both of the girls somehow misplace their vanities.
So his Thing doesn't go away. But it doesn't keep getting worse either. No one asks about it because by now they all know each other's stories. He doesn't have to explain to them that after his mother died his father couldn't look at him for two weeks. Or how looking at his reflection makes him sick and angry and sometimes violent.
He has his bad days, they all do. But it will always be one of those Things They Don't Talk About. It's on the list.
Stiles has a thing about mirrors. He can't stand the sight of his own face. Maybe one day, when he forgives himself, it will get better.