Bug bites, then blisters - related?

Total weirdness. Last weekend we were gardening and my son (21 m) got bitten a few times by black flies. He had a nasty reaction and scratched at them a lot so they became really red and bloody from being opened. I treated them like any other wound and kept him inside.

Then, this weekend we went camping not realizing that after over a month of rain the mosquitoes would be out in full force and boy, were they! We got eaten alive and came home early. They weren't even deterred by the smoke from our campfire or the loads of citronella repellent we put on every hour. My son got the worst of it, on his arms and legs.

Over Saturday night he developed more tiny red bumps that looked like mosquito bites on his face and a few on his hands, I assumed that a mosquito got into our bedroom and snacked on him while we were sleeping. However, he has now developed little clusters of blisters at the bite sites, not at all spread like a generalized rash. The most prominent ones are on the backs of his hands, the back of one leg, and his knees.

I'm really confused because I don't know if this is a reaction to mosquito bites, poison ivy (though we were very careful to keep him out of the undergrowth), or maybe chicken pox? Since it's all happening at the same time it's really hard to tell. Add to that his black fly bites, which look pretty nasty as they're in the scratched-up-but-healing stage and my poor kid looks like he's been through the wringer. The weirdest thing is he has nothing at all on his trunk, his genitals, or his butt. I thought CP generally started on the trunk, and he's had no fever, so now I'm not sure what to think.

Does anyone know of a fluid-filled blister reaction to insects? I'm >< this close to taking him to the doctor, but I'm a little afraid of getting the one I don't like who gave me a huge guilt trip for not getting my son the CP vax at his one-year checkup.

Advice appreciated. Thanks!