When dogs eat pistachios, there isn’t an immediate danger to your canine companion, but consumption should be regulated for a number of reasons.
Can Dogs Eat Pistachios?
There is no serious harm if dogs eat pistachios but they aren’t highly recommended as a snack or a treat of “human” food. Although these popular nuts do contain a good amount of protein and fiber, which can help dogs in various ways, there is also a high level of fat in pistachios. Any type of human food snack should only be treated as an occasional treat since your dog’s normal diet will provide all of the nutrients they need. That being said, pistachios should generally be avoided, as there are plenty of other “treats” that don’t pose the same health risks when eaten in excess. 
Particularly in the case of pistachios, the smell is highly appealing to dogs, who will likely try to munch on them if they are left out on a table. Also, once your dog has a taste for pistachios, it may be hard to dissuade them from eating in the future, which could be dangerous!
Health Benefits of Dogs of Pistachios
If your dog is occasionally given a few pistachios, it isn’t overly dangerous, but the negative impact on your dog will be greater than any benefit they happen to get from the dietary fiber or fat content in these popular nuts. One of the main reasons that pistachios are popular is due to their high omega-3 fatty acid content, but in dogs, this can quickly lead to obesity. Essentially, the fat intake of your dog should be closely monitored, and eating pistachios is not a good way to do that! 
Furthermore, it is well known that when dogs eat pistachios regularly or eat a large amount in one sitting, it can often cause severe gastrointestinal distress. This is partially due to the fat content, as well as the dog’s inability to digest certain proteins found in these nuts. This is in addition to the dangers of your dog eating high levels of salt or other chemicals that are often added to these nuts to flavor them.
Word of Caution
Pistachio poisoning is a real problem for canines who eat large amounts of pistachios, due to the potential presence of Aspergillus mold in these nuts. This mold produces a particular type of aflatoxin that is highly dangerous to dogs and can increase the risk of pancreatitis, jaundice, liver failure, vomiting, and loss of appetite. While not all pistachios will contain this mold, or the toxin, as mentioned earlier, it is best for your dog to avoid eating these nuts altogether.