There is no perfect answer for this question. What I have been told to do when puzzling out my dreams is to think about what the act of combing your hair means to you. Is it some sort of ritual of yours or a tradition from when you were a kid? Did someone special always brush your hair. Another thing to think about is who was combing your hair. Think about all these things and what they mean to you, hopefully the meaning will become more clear!
Maybe you miss your mother.
It is just a dream, it stands for nothing, don't take it seriously, take it easy.