http://experts.about.com/q/Ask-Veter...-pistachio.htm
Pistachios can be highly toxic to dogs.
---they have been known to cause symptoms as mild as diarrhea/vomitting, to severe as seizuring and hind end paralysis. Your veterinarian will want to do some bloodwork to comfirm whether or not a toxicity is present. If there is, activated charcoal will be given orally, to absorb any toxins in the blood stream and IV fluids will be given for 24-48 hours to flush the system out.