sting or some kind of bite

A couple months ago Lou Lou woke me up in the middle of the night itching bad, I turned the light on to find her whole head swollen and eyes almost swollen shut, so at 4am we were off to a vet. The vet said that it was some kind of sting or insect bite. He gave a shot and some anobotics and instructions to give benadryl. I searched the fenced in yard for any kind of nest or anything with no luck. Yesterday I went to get Lou Lou out of the fenced in yard and her right eye was swollen again. So I called the vet and they said give her benadryl and watch her breathing. So I woke up every 4 hours last night to shove benadryl down her throat and she looks better today, almost back to normal. I couldn't find anything in the yard again. We live in Michigan, has anyone else had a problem like this and figured up what it was that was biting their dog. Winchester never has any problems and the kids play out their too with no problems. I know that I may never figure this out and to always have benadryl on hand for my high maintance dog. With Lou Lou there is always something, she keeps us on our toes!

Thanks,
Heather :)

Fenway has been stung by bees or hornets before. He was digging in the dirt & they came out from the ground & bit him (bit me too). Maybe you have a bee or hornet issue?

I didn't think to check the ground, which would make sense for her, she has been digging in our woodchips and there is a small space between the dog kennel and fence were she could fit, I will check there. Winchester doesn't dig so he wouldn't get bite! Thanks! Heather :)