[Hypersensitivity (allergy) and infection]

In this subject, we would attempt to discuss some specific and non-specific mechanisms involved in immunity as well as hypersensitivity reactions against to infectious agents. Figure 1 presents a simplification of the response of allergic patient to microorganisms. Immunity, hypersensitivity and unresponsiveness to different antigens of the same infectious agents can occur simultaneously. For example, a patient who is sensitized and partially protected to toxins and other antigenic components of an infectious agents can be allergic to harmless components of the same organism. Sufficient exposure to the infectious agent may cause an allergic as well as an infectious disease. An allergic component of an infectious disease is suspected when the symptoms are unusually severe, protracted or occur in a known allergic patient. Modification of the hypersensitivity reactions becomes an important part of the treatment of the infection.