Yesterday evening, Steve started having some diarrhea (great, the giardia is probably back!). As it was getting late in the evening and I didn't want to be up all night with a poopy puppy, I gave him 1/2 of an Immodium (he's had it before w/o problems).
Within 15 minutes, he started running around shaking his head frequently. And then he started rolling on the carpets frantically. I didn't link this to the Immodium at all. We went to bed and usually he settles right down to sleep, but he continued his frantic head shaking, rolling, and then started panting really loudly. I got up and took him in to the kitchen to get a look at him under a strong light.
He was covered in welts under his fur, and his eyes were swollen almost shut, and his tongue was protruding. I had Benadryl on hand, so crushed one up and forced it down while getting ready to take him to the ER. But within minutes, he started getting better, so we didn't go.
I got up several times in the night to look at him and he was fine, and is fine this morning.
I've never had a dog react like that before. There was nothing else he ate or got into that could have caused it, though. Weird, huh?