Lincoln goes to the hospital and we're all baffled

About a month and a half ago Lincoln woke up with a "bug bite" just below his knee.  It was annoying, but we thought not much of it as, well,  it happens.  The weather had been warmer again, kids had been playing outside soaking up every last minute of comfortable weather, we figured something got him there.  It was a little swollen, which is the norm for him.

But the next day it was really swollen.
And the third day it was gone.

Or rather, he called me in and said "mom-my bug bite moved!"
Huh?
It had moved up on his thigh, no sign of anything where that "bug bite" had been.
It was obviously not a bug bite.

Then he mentioned that he had a few more "bug bites" on his back and one on his arm.
Hmmm....

We kept a close eye on him, and after two days he had broken out in some pretty serious hives.

All over.

It was bad enough that we took him in to get checked out.  The dr we saw said it looked like something stemming from an oral allergy, but he hadn't had anything new, so we were a bit mystified.  We went the prednisone and benadryl route, saw improvement over the next few days and made an appointment with the first allergist that had a quick opening.
Basic food allergy testing revealed a big fat nothing.
I think the dr thought I was disappointed that he didn't have an answer for me, which I suppose it would have been convenient if he did, but mostly I was just happy that we could rule out those things as an issue.  Totally revamping Lincoln's eating was not something I wanted to mess with!

Fast forward two weeks.
"Mom, I feel kind of itchy."
Hmm.  A spot.  Another spot.

And then they started cropping up on his scalp.

They just kept coming.

Over about 8 hours they had gotten so bad that we knew this wasn't one to just wait out.

This was bad enough that we headed for the ER.  Which was a good thing, as over the course of the nearly an hour drive, he continued to get worse.
The crowning moment was when Aaron and Lincoln walked in, started the check in process (where it's always nice and calm and slow paced unless you have someone obviously dying), and upon them questioning if the reaction was severe Lincoln proceeded to puke all over the desk.  Nice.

The good news is he didn't die.
Really.
He ended up anaphlyactic, requiring two shots of epinepherine to calm the reaction because the first one just wasn't cutting it.
Some time in the PICU, some work with cardiologists after concern came up about his heart rhythms, and a bunch of totally baffled drs consumed the next couple of days.
Never a dull moment!

His poor face was so swollen!

He did thoroughly enjoy his stay in the hospital once he was feeling a little better.  The day I was there with him he was so excited to show me the call button for the nurses.  He said "watch this mom!  It's like they are servants!"  Um, well, not exactly so let's quit pushing that button kiddo!  They were sweet as could be and really spoiled him.  And while he was there he got a visit from a few of the Utah Jazz players, the Jazz Bear and a few of the dancers.
(not sure if this will work, but HERE at 2:30 is Lincoln)
Add to that free access to tv and video games and a menu to pick meals and snacks from and he was living pretty large.

All's well that ends well though, we've been in the clear for a few weeks.  We do keep epi pens on hand now just in case, especially since we have no clue what cause this or what could cause it again, but thankfully we haven't had need for them at this point.
We are still completely stumped.  We get to go do some follow up with and allergist and immunologist at the end of the week, so maybe we will get an idea there.  The weirdest thing is that there is a possibility that this all may have been due to a virus.  Strange.