Dave, you are lucky to have such a fast response to your medical emergency. Hornets are NASTY!
They get really aggressive if you try to wave them away or swat at them...they just come right
after you. I had an in-ground colony under the roots of a lightning-struck tree in my front yard.
I didn't know until the tree guys got stung when they took the tree down. My neighbor and I
spent a couple hours soaking the ground with several different killing products, and spraying
the hornets directly when they came out to fight. We finally apparently got the nest saturated,
although we couldn't see it. I am SO glad they are gone!

N.