A guest with a milk (dairy) allergy orders a dish. Which of these hidden ingredients could still contain milk and cause a reaction?

解析

Milk allergens hide in ingredients such as butter, whey, casein, and many creamy sauces, so staff must read labels and recipes carefully. Black coffee brewed with water and served over ice, extra-virgin olive oil, and vinegar with salt and pepper carry no dairy protein. Knowing hidden dairy sources is essential to protect a milk-allergic guest.