Experimental evidence in the last decades show that iron is a fundamental element for normal development of the immune system. Its deficiency affects the capacity to have an adequate immune response. The role of iron in immunity is necessary for immune cells proliferation and maturation, particularly lymphocytes, associated with the generation of a specific response to infection. The body has the capacity to reduce the iron availability to be consumed by infectious elements by proteins such as transferrin and lactoferrin. Also, iron is essential for the proliferation of bacteria, parasites, and neoplastic cells. Thus excess iron could potentially facilitate the development of infections and the invasion of tumoral cells. The immune system has bacteriostatic mechanisms that reduce the availability of the metal, interfering with bacterial growth. Additionally the system uses iron as the intermediary in the production of bacteriostatic cells.