When Mason kissed Alex in Wizards vs Werewolves, why didn't Alex turn into one??

Didn't 你 hear this in the episode? It 说 that that only happens with "mutts", like the girl Justin dated. And apparently Mason was a "purebred"

Alex asks Mason this in Transylvania.

Alex: Hey, I've been meaning to ask 你 something. I thought when a werewolf kisses a non-werewolf they turn into a werewolf.
Mason: That's only with mutts. I'm a purebred.
Alex: Oh. Did 你 hear that, Justin? My boyfriend's a purebred!

I think that's all the explanation necessary :D

Mason was a pure bred he 说 that only happens to mutts.Like when Justin dated Isabella,she was a mutt so when she kissed him he turned into one.

Only girls 狼人 can turn a boy into Werewolves. That is the rule.