When the immune systems cause harm to the body, it is referred to as a hypersensitivity. There are two categories of adaptive hypersensitivities: immediate hypersensitivity and delayed hypersensitivit...When the immune systems cause harm to the body, it is referred to as a hypersensitivity. There are two categories of adaptive hypersensitivities: immediate hypersensitivity and delayed hypersensitivity. Immediate hypersensitivities refer to humoral immunity (antigen/antibody reactions) causing harm. Delayed hypersensitivities refer to cell-mediated immunity (cytotoxic T-lymphocytes, macrophages, and cytokines) causing harm.
An allergy is an adaptive immune response, sometimes life-threatening, to an allergen. Hypersensitivity reactions are classified by their immune mechanism.