Cashews are not poisonous to dogs. Cashews are a good source of fiber and nutrients, such as antioxidants, omega-3 fatty acids, minerals and vitamins.
However, cashews are high in sodium, fat and calories. For these reasons, a disadvantage of regular consumption of cashews by a dog is weight gain. Excessive weight in a dog can increase its chances of developing pancreatitis. Because cashews are high in phosphorus, they can cause bladder stones in dogs. Another disadvantage is that cashews may cause allergic reactions in some dogs.
It is fine to let dogs eat a moderate amount of cashews as an occasional treat. However, never feed a dog walnuts or macadamia nuts. These nuts are toxic for dogs.