Lentils are the most common cause of legume allergy in Spanish children and have a well-established cross-reactivity triad with chickpeas and peas — about 69% of people allergic to one are allergic to the others. Lentils contain two important allergens: a vicilin protein recognised by 77% of allergic individuals' immune systems, and an LTP (lipid transfer protein) that is heat-stable and cross-reacts with the primary peach allergen.

The LTP connection links lentil allergy to the broader LTP syndrome involving peach, apple, cherry, grapes, and nuts. One of the two main lentil allergens is reduced by cooking (though not fully destroyed), which is why reactions to well-cooked lentils can be milder than to undercooked ones. Lentils are increasingly common in pasta, gluten-free flour blends, and plant-based meat alternatives.