Its over quite a large area too
It looks like scratches to me so I am not help at all.
You're welcome.

He is insistent that no one or no thing has touched him
it looks like deep scratches, welt where the bleeding is.
He can't feel any pain I have poked him repeatedly
<<sacks Tee from official Mnet diagnosis board>>
Maybe there was bugs in the snow. They were probably prehistoric.
You're welcome too.
Nothing useful to add but impressed by the inserting photos thing, is that new? <luddite>
It's been here a little while. It's a special picture topic. Mostly used for pretty things.
Look Mnetters, I need theories. Can you imagine asking a GP what it is? They'll think I flay him!
In all seriousness, it looks a bit like the eczema. Sometimes my son's sort of looks like that.
Coco, just popped up to tell ds your theory. He's just as happy to wake up a dinosaur as a zombie.
~Looks like scratch marks, it really does.
Ok thanks 
What I think is that there was something in the snow that got shoved down there, small stones, maybe twigs.
As the snow froze the skin a bit he didn't feel the scratches.
<nods wisely>
But can eczema simply start one day out of no where?
I am prepared to get out the Immac if it was a werewolf.
It looks exactly like he's been scratched. More like a dog scratch.
Zombie has never had spots that look like that. She thinks dinosaur is more likely.
:: helpful not ::
I would have to agree with JKSLtd. Something was in the snow and scratched him.
Put some stuff on it, you know, anti-germ stuff. And some plasters.
I have sprayed him and left it uncovered to go scabby.
It was totally fresh snow. I am leaning toward a snow related injury, but there wasn't anything in the snow.
So in order of scenarios
Snow
Dinosauritus
Zombification
I vote Dinosauritus. For sure. He'll be 100 tons by morning. And green.
Oh good grief, do the Sporners know the picture topic exists?
It may lift the klaxon to a whole new level...
OhMyNoReally
Mon 14-Jan-13 21:25:43
Looks like carpet burns, but not sure you can get that from snow. It also looks like the marks I had when attacked by a goose as a child.
SecretNutellaFix
Mon 14-Jan-13 21:28:11
Was he rough-housing with Hully by any chance?
I used to end up with those when Kes used to jump all over me.