What are you lot like??!! I actually have tears in my eyes now!!

Scientific explanation is what you asked for-oh, I'm going to enjoy this- and that is what you shall have! Dogs have small glands on the pads of their feet, eccrine glands. The secretion from these, mostly water, helps to keep the walking surface in good condition. The more common name for the glands is sweat glands or eccrine sweat glands. Dogs like to lick this off because of the taste and you are simply smelling your dogs stale body odour!! (I wonder if you enjoy each other's armpitts too!!!)