What causes certain foods to trigger allergic reactions?

When someone has a food allergy, their immune system mistakenly identifies a specific food protein as a threat. The first time they eat the food, the immune system produces IgE antibodies against that protein and stores them on mast cells. On subsequent exposures, the food protein binds to those IgE antibodies, triggering mast cells to release histamine and other chemicals. This release causes symptoms ranging from hives and swelling to anaphylaxis in severe cases. Common culprits like peanuts, shellfish, and milk contain specific proteins that are particularly prone to triggering this mismatch. Genetic factors influence susceptibility, and early childhood exposure patterns may affect whether tolerance or sensitivity develops. The exact reason some proteins provoke immune responses while others do not is still being researched.