What Are Allergies?
Allergies are an abnormal response of the immune system.
People who have allergies have an immune system that reacts
to a usually harmless substance in the environment. This
substance (pollen, mold, animal dander, etc.) is called
an allergen.
Allergies are a very common problem, affecting at least
2 out of every 10 Americans.
What Happens During an Allergic Reaction? When a person 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 bind the allergen.
2. The antibodies attach to a form of blood cell called a mast cell. Mast cells
can be found in the airways, in the GI tract, and elsewhere. The presence of
mast cells in the airways and GI tract makes these areas more susceptible to
allergen exposure.
3. The allergens bind to the IgE, which is attached to the mast cell. This
triggers a reaction that allows the mast cells to release 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
likely occur in the eyes, nose and lungs. If the allergen
is ingested, the allergic reaction often occurs 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.
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, 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 response to the allergen is intense and affects the whole body.
It may begin with the sudden onset of itching of the eyes or face and progress
within minutes to more serious symptoms, including abdominal pain, cramps,
vomiting, and diarrhea, as well as varying degrees of swellings that can make
breathing and swallowing difficult. 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. |
