Last weekend was my club's agility trial. Oscar did two runs on Sunday morning, and about 2 PM I called DBF Steve to come get him, because I was working teardown. I got home about 6:30 PM, and Oscar's eyes were so swollen that one of them was completely shut. I tried holding a cold pack on his face, but he was not happy with that, so at 7:30 PM I gave him 2 benadryl tablets. That seemed to help and both eyes looked better, but he was rubbing his body against the sofa. His sides, legs, chest and neck were covered in hives. He was otherwise OK so I decided to wait until morning and take him to his regular vet. This was the start of a long night for us. He would try to sleep but the itching must have been unbearable. Then he would cry to go outside. The only time he seemed to be comfortable was when we were out walking. So we went for 4 or 5 walks. Luckily, the weather was nice and it was a beautiful night. At about 5 AM we both finally went to sleep. Oscar's hives seemed greatly reduced. I got an appointment for him at 1:50PM Monday. I could have had an earlier appointment with a different vet, but I wanted Oscar to be seen by his regular vet. By the time I took him in, the hives were almost gone. His fur felt different, but the vet told me to simply continue with the benadryl for two more days. There was also a veterinary student intern who attended Oscar's exam. I left for work just before 4 PM Monday. Oscar seemed all right, with just a few small hives here and there. At 4:30, Steve got home and called me at work. Oscar was full of huge hives. I called the vet office, and Oscar's regular vet had left, but I got an appontment for him with another vet as soon as Steve could get him there. Oscar got subcutaneous fluids to flush out the toxins, a shot, and prednisone pills. We were also to continue the benadryl. Steve said that when the same vet sudent saw Oscar, who had seemed fine about 3 hours earlier, she had a look of horror on her face. My poor Oscar did nothing but sleep for 2 days. He usually has agility class on Tuesday, but I left him home. I went to watch the class and took Mali because she has Rally Obedience class after Oscar's class. I could not bear to watch agility class. I was worried about Oscar. We left before Mali's class even started. Oscar is pretty much back to normal. He finished the prednisone but still needs to go out more often than usual. I hope this episode was not triggered by something at the training club facility, but that is not likely. He has been taking classes there, off and on, for 4 years. I am stumped as to what else could have brought this on. My best guess was a spider bite, but I don't understand how he got better and then worse. Has anyone experience something similar? If so, did you ever figure the cause?