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Something in the Air: Airborne
Allergens
Symptoms of Allergies to Airborne Substances
The signs and symptoms are familiar to many:
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Sneezing often accompanied by a runny or clogged nose
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Coughing and postnasal drip
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Itching eyes, nose, and throat
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Allergic shiners (dark circles under the eyes caused
by increased blood flow near the sinuses)
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The "allergic salute" (in a child, persistent
upward rubbing of the nose that causes a crease mark on
the nose)
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Watering eyes
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Conjunctivitis (an inflammation of the membrane that
lines the eyelids, causing red-rimmed, swollen eyes, and
crusting of the eyelids).
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In people who are not allergic, the mucus in the nasal passages
simply moves foreign particles to the throat, where they are
swallowed or coughed out. But something different happens to
a person who is sensitive to airborne allergens.
As soon as the allergen lands on the mucous membranes lining
the inside of the nose, a chain reaction occurs that leads the
mast cells in these tissues to release histamine and other chemicals.
These powerful chemicals contract certain cells that line some
small blood vessels in the nose. This allows fluids to escape,
which causes the nasal passages to swell, resulting in nasal
congestion.
Histamine also can cause sneezing, itching, irritation, and
excess mucus production, which can result in allergic rhinitis
(runny nose). Other chemicals made and released by mast cells,
including cytokines and leukotrienes, also contribute to allergic
symptoms.
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