Allergic reactions to food
1. Introduction
Allergic reactions to food can be immediate and severe, or they can develop over time. The symptoms of an allergic reaction depend on the type of allergy and the amount of allergen that has been consumed. Allergic reactions can be life-threatening and need to be treated immediately. The most common types of food allergies are to cow’s milk, eggs, peanuts, tree nuts, fish, shellfish, soy, and wheat.
2. Allergic reactions: an overview
Allergic reactions are hypersensitivity reactions of the immune system to foreign substances (allergens) that are normally harmless. Allergens can be inhaled, ingested, or injected and they trigger an immune response that leads to the release of chemicals such as histamine. These chemicals cause the symptoms of an allergic reaction. The most common allergens are proteins from foods, drugs, insect venom, and latex.
Most allergic reactions are mild, such as a runny nose or a rash. However, some reactions can be severe or life-threatening. Severe reactions are called anaphylaxis and they occur when the airways narrow and breathing becomes difficult. Anaphylaxis can be triggered by any allergen, but the most common triggers are peanuts, tree nuts, fish, shellfish, milk, eggs, and wheat.
3. Anatomical and physiological background
The cells involved in allergic reactions are mast cells and basophils (granulocytes). These cells contain granules that contain histamine and other chemicals that are released when the cell is stimulated by an allergen (1). The allergen binds to IgE antibodies on the surface of the mast cell or basophil. This triggers a chain reaction that leads to the release of histamine and other chemicals from the granules (2). Histamine causes the symptoms of an allergic reaction by binding to receptors on blood vessels, smooth muscle cells, and nerves (3).
4. Pathophysiology of food allergies
The pathophysiology of food allergies is not fully understood. However, it is thought that food allergies develop when the immune system mistakenly identifies a protein in food as harmful (4). The protein is then taken up by antigen-presenting cells in the gut and presented to T-cells in the lymph nodes (5). This triggers a cascade of events that leads to B-cells producing antibodies against the protein (6). These antibodies then bind to mast cells and basophils in the gut which leads to the release of histamine and other chemicals (7). The symptoms of an allergy develop when histamine binds to receptors in blood vessels, smooth muscle cells, and nerves (8).
5. Conclusions
Allergic reactions are hypersensitivity reactions of the immune system to foreign substances that are normally harmless. Allergens can be inhaled, ingested, or injected and they trigger an immune response that leads to the release of chemicals such as histamine. These chemicals cause the symptoms of an allergic reaction. Most allergic reactions are mild, but some can be severe or life-threatening. The pathophysiology of food allergies is not fully understood but it is thought that they develop when the immune system mistakenly identifies a protein in food as harmful.