We have 2 Mini Foxies (1F & 1 M), our female loves to lick the bottom of my foot when I put her in our bed at 3am in the morning, when she is satisfied she lays down on my foot and goes off to sleep.

Our Male sits with me on my lounge and licks my legs, again once he is satisfied he also lays down and goes to sleep, however he doesn't lick if I am wearing leggings, jeans or track pants. So this seems to be a durrant.

They are Brother and Sister born 1 year apart (2 different litters, but same parents).

So in conclusion I would say it is definitely a soothing thing, a bit like a baby with a dummy.