How the Body Reacts to a Food Allergy

Understanding Allergic Reactions

An immediate allergic reaction involves two actions of your immune system. Your immune system produces immunoglobulin E (IgE), a type of protein that works against a specific food. This protein is called a food-specific antibody, and it circulates through the blood.
The food-specific IgE then attaches to mast cells, which are found in all body tissues. They are more often found in areas of your body that are typical sites of allergic reactions. Those sites include your:
  • Nose
  • Throat
  • Lungs
  • Skin
  • Gastrointestinal (GI) tract.
Generally, your immune system will form IgE against a food if you come from a family in which allergies are common -- not necessarily food allergies, but perhaps other allergic diseases, such as hay fever or asthma. If both of your parents have allergies, you are more likely to develop a food allergy than someone with one parent with allergies.
If your immune system is inclined to form IgE to certain foods, you must be exposed to the food before you can have an allergic reaction. This is what happens in a typical allergic reaction:
  • As the specific food is digested, it triggers certain cells in your body to produce a food-specific IgE in large amounts. The food-specific IgE is then released and attaches to the surfaces of mast cells.
  • The next time you eat that food, it interacts with food-specific IgE on the surface of the mast cells and triggers the cells to release chemicals such as histamine.
  • Depending upon the tissue in which they are released, these chemicals will cause you to have various food allergy symptoms.
Food allergens are proteins within the food that enter your bloodstream after the food is digested. From there, they go to target organs, such as your skin or nose, and cause allergic reactions.
An allergic reaction to food can take place from within a few minutes up to an hour. The process of eating and digesting food affects the timing and the location of a reaction. For example:
  • If you are allergic to a particular food, you may first feel itching in your mouth as you start to eat the food.
  • After the food is digested in your stomach, you may have GI symptoms, such as vomiting, diarrhea, or pain.
  • When the food allergens enter and travel through your bloodstream, they may cause your blood pressure to drop.
  • As the allergens reach your skin, they can cause hives or eczema.
  • When the allergens reach your lungs, they may cause asthma.
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