Well you're certainly not alone! If you try to google "child licks hands", google completes the phrase after just typing in "child licks".
There are theories that it's related to autism, and many say it's not related to a disorder, but rather, anxiety.
It will be informative what your doctor says.
Hi there. Sorry you have this worry with your child. I know first hand how these worries can produce anxiety in a parent. I'm very glad you are seeing her doctor to discuss this to put your mind at ease.
It is hard to say. I know that sensory integration disorder (and most autistic kids have sensory issues although you can have sensory integration disorder without autism) do tend to have this impulse. Often kids must smell as well.
But again it is impossible to really understand what is going on from this snippet of information. When is your doctor's appointment?
Does she have any problems with speech and communication? If not,
have you asked her why she is doing this?
It would be interesting to see how she responds.