What is the main difference between allergens and antigen-stimulated antibodies? Please explain their respective positions and action mechanisms.

Allergens are actually antigens that can cause allergic reactions. When common antigens come into contact with the body, they will cause the body's immune response and produce antibodies to remove them. Allergen is the same as the common antigen when it comes into contact with the body for the first time, but the antibody formed at this time will exist in the surface epithelial cells of blood cells after completing the immune reaction, instead of in serum under normal circumstances, and an allergic reaction will occur when the body comes into contact with the same allergen for the second time.