Food Allergy

Food allergies involve two parts of your immune system. One is immunoglobulin E (IgE), a type of protein called an antibody that moves through the blood. The other is mast cells, which you have in all body tissues but especially in places like your nose, throat, lungs, skin, and digestive tract.

The first time you eat a food you're allergic to, certain cells make a lot of IgE for the part of the food that triggers your allergy, called an allergen. The IgE gets released and attaches to the surface of mast cells. You won't have a reaction yet, but now you're set up for one.

The next time you eat that food, the allergen interacts with that IgE and triggers the mast cells to release chemicals such as histamine. Depending on the tissue they're in, these chemicals will cause various symptoms. And since some food allergens aren't broken down by the heat of cooking or by stomach acids or enzymes that digest food, they can cross into your bloodstream. From there, they can travel and cause allergic reactions throughout your body.

The digestion process affects the timing and the location. You may feel itching in your mouth. Then you may have symptoms such as vomiting, diarrhea, or belly pain. Food allergens in your blood can cause a drop in blood pressure. As they reach your skin, they can trigger hives or eczema. In the lungs, they may cause wheezing. All of this takes place within a few minutes to an hour.

From WebMD