How long ago did he eat them? And how many did he eat?
OK, thanks for the information.
Raisins are not always toxic to dogs, and there doesn't appear to be any rhyme or reason as to which ones and how many might cause a problem. We still don't know what the actual poison involved is.
When they do cause a problem, however, it is very serious. Ingestion can lead to kidney failure.
Since your dog is showing signs of toxicosis (vomiting and diarrhea), you need to get him checked out as soon as possible to have his kidney values checked. He may require aggressive IV fluid therapy for his kidneys to recover if they are compromised. I would get him in as soon as you can, since both of those signs can indicate a big problem with raisins.
Hope that helps. Please let me know if you have any other questions.