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Allergy Basics
What are allergies?
Allergies are an overreaction of the immune system. People who have
allergies have a hyper-alert immune system that overreacts to a substance
in the environment called an allergen. Exposure to what is normally a
harmless substance, such as pollen, causes the immune system to react as
if the substance is harmful.
Allergies are a very common problem, affecting at least 2 out of every 10
Americans.
What happens during an allergic reaction?
When a person
with a hyper-alert immune system is exposed to an allergen, a series of
events takes place:
1.
The body starts to produce a specific type of antibody, called IgE,
to fight the allergen.
2.
The antibodies attach to a form of blood cell called a mast cell.
Mast cells are plentiful in the airways, and in the GI tract where
allergens tend to enter the body.
3.
The mast cells explode releasing a variety of chemicals including
histamine, which causes most of the symptoms of an allergy, including
itchiness or runny nose.
If the
allergen is in the air, the allergic reaction will occur in the eyes,
nose, and lungs. If the allergen is ingested, the allergic reaction will
occur in the mouth, stomach, and intestines. Sometimes enough chemicals
are released from the mast cells to cause a reaction throughout the body,
such as hives, decreased blood pressure, shock, or loss of consciousness.
This severe type of reaction is called anaphylaxis and can be
life-threatening.
What are the symptoms of allergies?
Allergy
symptoms can be categorized as mild, moderate, or severe (anaphylactic).
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Mild reactions include
those symptoms that affect a specific area of the body such as a rash or
hives, itchy, watery eyes, and some congestion. Mild reactions do not
spread to other parts of the body.
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Moderate reactions
include symptoms that spread to other parts of the body. These may
include itchiness or difficulty breathing.
A severe
reaction, called anaphylaxis, is a rare, life-threatening emergency in
which the body's response to the allergen is sudden and affects the whole
body. It may begin with the sudden onset of itching of the eyes or face
and within minutes progress to more serious symptoms, including varying
degrees of swellings that can make breathing and swallowing difficult,
abdominal pain, cramps, vomiting, and diarrhea. Mental confusion or
dizziness may also be symptoms, since anaphylaxis causes a quick drop in
blood pressure.
Does everyone have allergies?
No. Most
allergies are inherited, which means they are passed on to children by
their parents. People inherit a tendency to be allergic, although not to
any specific allergen. When one parent is allergic, their child has a 50%
chance of having allergies. That risk jumps to 75% if both parents have
allergies.
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