Yes, typically pistachio sauce contains milk, often in the form of condensed milk.
While some variations might use almond or coconut milk as a substitute, traditional pistachio sauces, especially those used in lattes or desserts, frequently include dairy. The provided reference specifically mentions that the pistachio latte's sauce contains condensed milk, which is not vegan. Therefore, if you are concerned about milk content, it's best to check the ingredient list of the specific pistachio sauce you are considering, or inquire about the ingredients if you are purchasing it from a cafe or restaurant.
