Last month we were packing the camper to go and a European paper wasp came at me. They're not as vicious as yellowjackets or bald faced hornets, but it's a wasp and my husband is allergic. Last year I got nailed 6 times by them, and their nests were EVERYWHERE, so this year I've made a very determined effort to kill every nest I find...and they're getting inventive. This particular wasp had built her nest in the corner of the rear stabilizer jack, which was down at the time. If she'd not come at me I would never have known she had a nest there, and come time to raise the stabilizer jacks, it might have been a worse case scenario as my husband is usually the one who raises the jacks.
Unlike yellow jackets and hornets, which have one big nest with a single queen, European paper wasps are ALL fertile, and each female will build her own nest and raise her own workers. If you kill her, you have to kill them all, because, again, for insects, wasps are pretty intelligent. They learn to recognize the ape (me) that threatens or removes their nests. I can't tell you how often I was harassed by wasps last year, because I was merely knocking the nests down rather than outright killing them.
When I spray them, I use the foaming spray and try to squash them once they've fallen to the ground. In the case of hornets and yellowjackets (gads they are vicious) if you harm a wasp rather than kill it outright, it produces a pheromone that summons every wasp in the vicinity to come attack you. So kill them quickly.
I usually wait until morning to hunt them down and spray the nests, when the air is cool and all the wasps are 'home' on their nest.
But if you can, try not to kill them when they're not in your sphere. They are important and relentless predators of all sorts of nasty bugs that go for your apples or your vegetables. Same goes for snakes, please, folks. I understand the instinctive fear of snakes but they are really great predators of rats and mice.
And finally, take an Epi Pen camping or whenever you go out where there may be wasps (this is if you're allergic). By the way, Epi Pens do NOT need refrigeration, I don't know why people automatically toss them in the fridge. Don't do that. They don't need cooling. And also, read the instructions on its use.