Pistachio nuts are not toxic per se to dogs. However, they are high in fat and can lead to an upset stomach and even pancreatitis in some cases.
Pancreatitis is an inflammation of the pancreas. The pancreas is a gland that produces and releases enzymes into the digestive track that aid in the digestion of food. When these same enzymes are activated while they are still in the pancreas, inflammation occurs and the enzyme start "digesting" the pancreas itself. Some common causes of pancreatitis are eating a lot of very fatty foods, obesity, steroid use and other diseases and conditions.
Symptoms of pancreatitis vary but include vomiting, diarrhea, anorexia, weakness or collapse, dehydration, shock, fever, depression, and upper abdominal pain. A dog may indicate abdominal pain by acting restless, panting, crying or wincing when picked up, shaking, standing with an arched back, or lying with the front end down and the rear end elevated, You can read about it in detail here:
What you might do is start feeding a bland diet of boiled chicken and rice for a few days and give pepto-bismol for a few day as well to help coat the stomach. Monitor Sofie for a few days and if she doesn't develop symptoms of pancreatitis, switch Sofie back to her regular food gradually over a couple of days.
Try not to let her get any more pistachios if you can. We all know how scrumptious they are. You might cut a hot dog up in paper thin slices to give her as a treat while you have the nuts.
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