Introduction Abnormal immune responses to proteins found in certain foods can cause allergic reactions when such foods are ingested by susceptible individuals. Such immune reactions are called food allergies, and the proteins which cause the reactions are called allergens. Foods such as milk, peanuts, eggs, fish, and shellfish are the ones that most commonly cause allergic reactions in the American population. Food allergy affects about 2% of children and about 8% of adults, and cause serious illnesses and in some rare cases even death. The immune system is made up of cellular and molecular components that can induce and maintenance tolerance to allergens. Various methods have been developed for the diagnosis and management of food allergies. In this paper, the immunological processes of allergic reactions are described giving the relevant anatomical and physiological parameters. Then an overview of pathophysiological features (clinical manifestations) of food allergies is given including their traditional and current diagnostic and management (or treatment) including the immunotherapeutic techniques. Finally, conclusions are given providing a generalized picture of the scope of work still needed to solve the problems of allergies to foods and also to other environmental, domestic, and occupational allergens. Mechanism of Immune Response to Food Allergies Allergic reactions are usually typed 1 hypersensitivity reactions and involve two arms of the immune system, namely mast cells and immunoglobulin E (IgE). In most cases, when a person ingests food that contains an allergen, the body produces large amounts of IgE specific to food that they had previously been exposed to. The IgE that is released has a high affinity for its receptor on mast cells in the tissues and basophils in the blood, both having mediators of inflammation in their cytoplasm. This process is called mast cell sensitization. On second and subsequent encounter with the same antigen, the IgE and its receptor FcεRI are crosslinked, resulting in the synthesis and release of cytokines and lipid mediators and also the release of granules in the cytoplasm which causes the allergic reaction. Figure 1 shows the sequence of events in immediate hypersensitivity. Immune system cells like T helper 1 and T helper 2 are involved during an allergic reaction to food. The T helper 2 subset is the one that leads to IgE production through B cells activation which involves cytokines such as I-3 and IL-13. Figure 1: Sequence of events in immediate hypersensitivity Depending on their structures, proteins or antigens that come into contact with the surface of the intestine are taken up by different cells which can lead to varied responses. The cells that can take up the proteins or the antigens include Peyer’s patches, Microfold cells, and epithelial cells or dendritic cells. Figure 2 shows the antigen uptake sites in the intestine or the gut. After the proteins are taken up by the immune cells, they are broken up or processed into peptides which can then be presented (by antigen-presenting cells, or APCs) to be recognized by immune activation cells. The generation of peptides from intact protein antigens involves modification of the native proteins and is commonly referred to as antigen processing. On the other hand, the di