These antibodies attach themselves to mast cells in the body, and when the person again eats the allergenic food, the proteins from it become attached to the IgE antibodies.

This causes the mast cells to degranulate, releasing histamine and other powerful chemicals. It is these chemicals that cause the symptoms of allergy.
See: The Signs and Symptoms

What is Anaphylaxis?

There is a name for the severe form of allergic reaction: anaphylaxis. This is an emergency medical event involving one or more of the body’s systems: respiratory, gastrointestinal (the gut), the skin and the cardiovascular system (e.g. a drop in blood pressure).

In an anaphylactic reaction, a person can lose consciousness with a drop in blood pressure. Anaphylaxis can be fatal, which is why food-allergic individuals and parents of kids with food allergies are instructed by allergists to avoid even trace amounts of specific allergens: e.g. peanut, nuts or mlk.

Allergic reactions are notoriously inconsistent. An individual might have a minor reaction on one exposure to a food (e.g. a cashew) but another time have anaphylaxis.

The risk of severe reaction is higher in those with asthma, and those who have had a previous serious reaction. That said, there are instances of anaphylaxis without asthma or previous serious reaction. So if a person is food allergic, there is always a risk of anaphylaxis. So far, there is no way of measuring this level of risk, but researchers are beginning to locate markers that may lead to a test down the road.

Top 8 Food Allergy Triggers (United States)
These “priority allergens” cause the majority of food allergy reactions:
• peanuts
• tree nuts (e.g. almonds, cashews, hazelnuts, pecans, walnuts)
• milk
• egg
• shellfish (shrimp, crab, lobster, mussels, clams)
• fish
• soy
• wheat

Top 11 Food Allergy Triggers (Canada)
These “priority allergens” cause the majority of food allergy reactions:
• peanuts
• tree nuts (e.g. almonds, cashews, hazelnuts, pecans, walnuts)
• milk
• egg
• shellfish (shrimp, crab, lobster, mussels, clams)
• fish
• soy
• wheat
• sesame
• mustard
• sulphites (Health Canada also lists these food additives as one of the common causes of reaction, though it is not a food protein.)

A Note on Food Intolerance: This sensitivity can cause gastrointestinal distress, but it does not involve the immune system or a reaction to the proteins in food. An intolerance is not an allergy.