It wasn't the wormer in our case. I think definitely something she chewed on. Funny you should mention plum stones. We have a couple of crab apple trees at the end of our garden and she goes mad for any decomposing fruit she can find. I have picked up any I can get too, but she can get behind the shed and I can't and I suspect there are a lot of these delicacies behind there! Yum! She really does eat anything. This week in training we are working heavily on 'leave it'!
One of mine was ill after a wormer the time before last. Both ends. Next time, I fed the tablet after a meal, rather than at the start, hoping it would slow the absorption. I have no idea if it helped, but we didn't have a repeat of the illness.
Charlie had a bout of vomiting the last time I gave him advocate (a topical skin applied flea and wormer). I can't 100% be sure it was that, but I think it was (I think he vomited the previous time too). I've swapped to a different wormer (he is due another treatment soon). Even if wormers do upset some dog's tummies, I believe it's better than leaving them untreated.
