I meant to respond to this earlier. My ferret, Rio, had a bad reaction to the Canine Distemper vaccine when I took him for his yearly shots, both rabies and distemper. I know that he had been previously vaccinated against rabies, but I wasn't sure if he had been vaccinated against Distemper. Since I was aware that some ferrets do react to the vaccination, I was not too freaked out when he did react. My vet was more astonished than I was, because he said this is the first time he has seen a reaction. Rio recovered in about an hour or so and was back to normal by the evening. I took Rio back for a Distemper booster shot about a month later. The vet chose not to pre-treat, instead to observe Rio's reaction to getting only one vaccine. If he had the same reaction, then in future we would know to pre-treat before giving him the distemper shot. Rio did not have an allergic reaction this time. We observed him closely for about twenty minutes - his previous reaction happened within 15-20 minutes of being vaccinated - and I continued to check on him for a couple of hours afterwards, but there was no reaction. In my case, it seems that the combination of rabies and distemper at the same time caused the allergic reaction. It may have been something else, but in future, we won't be taking any chances, and we'll give him his shots on separate visits. Hope that helps. Inez -owned by Rio and Lola [Posted in FML 5484]