Which of the following has not been shown to cause allergic reactions?

Lettuce is the correct choice because it is not commonly associated with allergic reactions. While many foods can trigger allergies, the most common allergens include peanuts, tree nuts (like pine nuts), and dairy products. These foods are well-documented to cause allergic responses in sensitive individuals.

In contrast, lettuce is generally considered safe for most people and does not typically provoke allergies, making it less likely to cause reactions. There have been some rare instances where individuals may experience sensitivities to lettuce, but these cases are exceptionally uncommon compared to the established knowledge regarding the allergenic potential of peanuts, dairy, and pine nuts.