What is the explanation for this rather peculiar behaviour? I read somewhere that they do it to get salt. really?
In dogs’ case, it’s to show love. In cats’, it’s because they just ate their shit - or a mouse.
Wolf cubs lick the muzzle of adults to encourage them to regurgitate food they had eaten outside of the den.
We have bred dogs to retain a number of behavioural traits of immature wolves.
So the dog is trying to make you vomit. Respectfully.
Social grooming, in a figurative and literal sense.
Cleaning each other is one way cats and dogs show each other affection. They don’t have the limbs to stroke and hug each other. Licking is likely to be pleasant to them, if only because it’s reminiscent of what their mother used to do to clean them. Compare it to the way apes will groom each other both for hygiene and bonding purposes.
My two male cats are gaytos and they’ll cuddle and lick each other even though they do not lack food, even less so salt. They both enjoy it and it seems to help them bond.