How Do Allergic Reactions Work ?
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 ,cells 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,and 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 you have two allergic parents, you are more likely to develop food allergy than someone with one allergic parent.
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.
As this 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 symptoms of food allergy.
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 within a few minutes to an hour. The process of eating and digesting food affects the timing and the location of a reaction.
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.
If you have a life-threatening reaction to a certain food, your health care provider will show you how to avoid similar foods that might trigger this reaction. For example, if you have a history of allergy to shrimp,testing will usually show that you are not only allergic to shrimp but also to crab,lobster,and crayfish. This is called “cross-reactivity.”
Another interesting example of cross-reactivity occurs in people who are highly sensitive to ragweed. During ragweed pollen season, they sometimes find that when they try to eat melons, particularly cantaloupe, they experience itching in their mouths and simply cannot eat the melon. Similarly, people who have severe birch pollen allergy also may react to apple peels. This is called the “oral allergy syndrome.”