Oh Mel... I have a friend who's little boy is also 3 and OMG he's a SHOCKER!! He started licking things in the past few months also and GROSS! He's ALWAYS been one to "taste" things and chew toys etc.... apparently like TMTM said it's a sensory thing. There are 4 groups of people, mouth and touch are the only 2 I can remember straight off the top of my head.. but the mouth explorers is exactly that... they MUST taste and feel the world with their mouths and touch well... I think Oskar might be a bit like that... touch and feel the world. Not overly helpful to you, but as he gets older you'll be able to redirect him a bit like TMTM suggested... sorry hun!