Swollen face

[lindapalm]

My son's lab went outside yesterday, only on the grass, no woods or weeds.  He came in and immediately his face started to swell.  They rushed him to the vet, and he received a shot, and is getting better.  My question is, what could have bit him, its 31 degrees outside, what would be alive in this weather?  They can't think of anything inside that would have given him a reaction.

[lindapalm]

I've never seen a bee or wasp out this time of year, but I guess its not impossible.  Possibly one was in the garage, where its a little warmer.  If it was a snake, it would have been just in the grass, as they have no bushes, rocks, etc. and the dog does not go beyond the electric fence. I don't think snakes are around in the winter, not sure.  Hopefully it was a one time thing.  Thanks Ginger899.

[ginger899]

I probably can't be much help because, being a Brit, the only things we have that could "bite" and cause suden swelling like that are bees wasps and hornets. We have adders too but they are rarely seen and hibernate in winter, though they often do come out to "sunbathe".
It depends on whereabouts you live, what kinds of things could possibly survive the cold, and bite like that. It is possible a snake was hibernating underneath something and was disturbed?
It is also possible a wasp could be still around hiding under something? I was seeing wasps here, still capable of stinging, though extremely sluggish, a few weeks ago when it was about the same temperature here....