C.M.
I have a 19 month old who has a tendency to chew on things until I saw this post I never thought much of it. I'm sure she's just doing it because A)babies put things in their mouth to explore them B) it probably is helping her tooth by teething on something and C) when we play we nibble her toes, hands, nose belly. I've noticed that she tries to nibble our feet when she wants to play and have attention. Oh yeah, my daughter Parker no longer has her nuk(binky) we took it away a little before 18 months.
PS. Our pediatrician said it's a good thing to send them to bed with a sippy of water, it helps them stay hydrated and put themselves back to sleep.
I hope this helps. ~C.