| When
the immune system decides that a particular food is harmful,
it may create specific antibodies to it. The next time
the individual eats that food, the immune system releases
large amounts of chemicals, including histamine, to protect
the body. These chemicals generate allergic symptoms that
can affect the respiratory system, gastrointestinal tract,
skin, and cardiovascular system. Today scientists estimate
that approximately 12 million Americans suffer from food
allergies.
In
food allergies, two parts of the immune response are
involved, according to researchers at the National Institute
of Allergy and Infectious Diseases. One is the production
of an antibody called immunoglobulin E (IgE) that circulates
in the blood. The other part is a type of cell called
a mast cell. Mast cells occur in all body tissues but
especially in areas that are typical sites of allergic
reactions, including the nose, throat, lungs, skin,
and gastrointestinal tract.
People
usually inherit the ability to form IgE against food.
Those more likely to develop food allergies come from
families in which allergies such as hay fever, asthma,
or eczema are common.
A
predisposed person must first be exposed to a specific
food before IgE is formed. As this food is digested
for the first time, tiny protein fragments prompt certain
cells to produce specific IgE against that food. The
IgE then attaches to the surface of mast cells. The
next time the particular food is eaten, the protein
interacts with the specific IgE on the mast cells and
triggers the release of chemicals such as histamine
that produce the symptoms of an allergic reaction.
If
the mast cells release chemicals in the nose and throat,
the allergic person may experience an itching tongue
or mouth and may have trouble breathing or swallowing.
If mast cells in the gastrointestinal tract are involved,
the person may have diarrhea or abdominal pain. Skin
mast cells can produce hives or intense itching.
The
food protein fragments responsible for an allergic reaction
are not broken down by cooking or by stomach acids or
enzymes that digest food. These proteins can cross the
gastrointestinal lining, travel through the bloodstream
and cause allergic reactions throughout the body.
Source
FDA Center for Food Safety and Applied Nutrition
Information About Food Allergies: www.cfsan.fda.gov/~dms/wh-alrgy.html
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