A cocktail can look simple and still carry real allergen risk. Egg white, dairy, nut syrups, flavored spirits, spice blends, beer, wine, foams, garnish oils, and house-made prep can all change what is safe for a guest. In a busy service, the problem is rarely one dramatic mistake. It is usually a small gap: an unlabeled syrup, a reused shaker, an outdated menu note, or a bartender forced to answer from memory.