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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:
The body starts to produce a specific type of antibody,
called IgE, to fight the allergen.
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.
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).
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.
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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