Oh they do this a lot and I think that tgtiffany is correct they do it because they like the smell of you, just like any other animal does ....Its not any concern .
My daughter does this sometime, she's 18 months...I think it's just they like your smell. I mean that's how they got to know you from the beginning you know? They couldn't see well, they could smell you and hear you, I think that's why she's doing it. I wouldn't be concerned about it though, it doesn't seem harmful even if there is a different reason for her doing it.