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For millions of Americans, "allergy
season" never ends. Colder temperatures that eliminate the problems of grass and
tree pollens also drive people indoors where they meet troublesome dust mites,
animal danders, and dust mites. Most indoor environments actually trap airborne
allergens where they can pose a risk to respiratory health.
Many people with allergic rhinitis also can be at
risk of developing allergic asthma. Symptoms to watch for are a persistent cough
or wheezing.
An allergist can evaluate asthma and allergy
symptoms, perform tests to determine the precise cause of the symptoms and,
together with you, develop a treatment plan that brings allergic reactions under
control. Sometimes allergy shots, also known as immunotherapy, can improve
natural resistance and decrease sensitivity to specific allergens. Allergy shots
also can prevent the development of allergic asthma.
If you suspect that an indoor allergen is causing
upper or lower respiratory symptoms, see your doctor. If tests show that a
specific allergen is causing your symptoms, there are steps you can take to
limit your exposure to such allergens. You should not try these tedious and
complex measures without first being tested to see if you actually are allergic.
House Dust Allergy
House dust is present even in clean homes. Allergenic components of house dust
are a major cause of year-round runny or stuffy nose, itchy, watery eyes and
sneezing for allergy sufferers. Dust allergy can also make people with asthma
experience wheezing, coughing and shortness of breath.
Why does house dust cause allergic reactions?
House dust is a mixture of many substances. Its content varies from home to
home, depending on the type of furniture, building materials, presence of furry
pets, moisture and other factors. A speck of dust may contain fabric fibers,
human skin particles, animal dander, microscopic creatures called house dust
mites, parts of cockroaches, mold spores, bacteria, food particles and other
debris. Of these, animal dander, house dust mites and cockroaches are the most
common culprits. A person may be allergic to one or more of these substances,
and, if exposed to the dust, will have an allergic reaction.
Is dust allergy a sign of a dirty house?
No. A dirty house can make a house dust allergy problem worse, however. Normal
housekeeping procedures may not be enough to get rid of house dust allergy
symptoms. This is because many of the substances in dust cannot be removed by
normal cleaning procedures. For example, no matter how vigorously you dust or
vacuum, you will not reduce the number of dust mites present deep within
carpeting, pillows and mattresses. Vigorous cleaning methods can put more dust
into the air making symptoms worse.
What are house dust mites?
Tiny microscopic creatures
called house dust mites are an important cause of allergic reactions to house
dust. They belong to the family of eight-legged creatures called arachnids. This
family also includes spiders, chiggers and ticks. Dust mites are hardy creatures
that live well and multiply easily in warm, humid places. They prefer
temperatures at or above 70 degrees Fahrenheit with a relative humidity of 75
percent to 80 percent and die when the humidity falls below 40 percent to 50
percent. They are rarely found in dry climates.
As many as 10 percent of the general population
and (in some regions) 90 percent of people with allergic asthma are sensitive to
dust mites. Recent studies in the
United States
suggest that at least 45 percent
of young people with asthma are allergic to dust mites.
Dust mite particles are just the right size to be
inhaled. They are found in the highest concentrations in pillows, mattresses,
carpeting and upholstered furniture. They float into the air when anyone
vacuums, walks on a carpet or disturbs bedding, but settle out of the air once
the disturbance is over. A dust mite allergic patient who sleeps for eight hours
every night spends one third of his life with his nose in direct contact with a
pillow loaded with dust mite particles!
There may be many as 19,000 dust
mites in one gram of dust, but usually between 100 to 500 mites live in each
gram. (A gram is about the weight of a paper clip.) Egg-laying females can add
25 to 30 new mites to the population during their lifetime. Mites eat particles
of skin and dander, so they thrive in places where there are people. Dust mites
don't bite, and cannot spread diseases. They are harmful only to people who
become allergic to them. While usual household insecticides have no effect on
dust mites, there are ways that allergic people can reduce exposure to dust
mites in the home.
Why is mold present in house dust?
Molds are commonly found in
outdoor air, and they come in any time you open a door or window. Any house can
develop a mold problem given the right conditions. You might not see it growing
on the walls, but it may still be present in your home. Molds require two
factors to grow indoors: (1) free moisture that can occur in the form of
relative humidity above 50 percent, leakage from pipes or foundations, or any
ongoing source of water; and (2) something to grow on. Molds particularly like
to grow on wallboard, wood or fabrics, but will grow virtually any place if they
are given a chance.
Molds spread by producing spores that can become
airborne. These spores end up in house dust where they grow. Dust from
mold-contaminated houses can cause allergy symptoms if a mold-sensitive person
inhales it.
Does house dust contain cockroaches?
As unappealing as it seems,
cockroach particles can be a component of house dust. This is most common in
older, multifamily housing and in the southern
United States
where complete extermination of
cockroaches is very difficult. Allergic individuals, particularly those with
asthma, will tend to have increased symptoms when they go into such houses.
Cockroaches require food and moisture to survive, so eliminating sources of each
can help reduce exposure. In cockroach endemic areas, the services of a skilled
professional exterminator will be required to keep cockroaches under control.
Is house dust allergy seasonal?
Yes. In the
United States
, dust mite populations tend to
peak in July and August, and their allergen levels stay high through December.
Mite allergen levels are lowest in late spring. Some dust mite-sensitive people
report that their symptoms get worse during the winter. That's because mite
fecal particles and pieces of dead mites, both of which trigger dust mite
allergy, are still present. Mold levels tend to peak during the summer months
depending on where you live since some tropical areas have molds year-round.
There is also evidence that cockroaches have a seasonal pattern, peaking in the
late summer.
Forced-air heating systems tend to blow dust
particles into the air. As they dry out over time, even more of the particles
become airborne. This does not account for the seasonal pattern, however, since
air blows through the same ducts during the summer when air conditioning is
used. People may have fewer symptoms from house-dust exposure during the summer
because they spend more time outdoors.
For these reasons, the terms "seasonal allergy"
and "perennial allergy" are being used less frequently. It is better to classify
symptoms as "intermittent" or "persistent".
How do I know if I have house dust allergy?
If you think you may have an
allergy to house dust, consult an allergist-immunologist. To pinpoint the cause
of your symptoms, the allergist may ask questions about your work and home
environments, eating habits, family medical history, frequency and severity of
symptoms, exposure to pets and a variety of other questions. Your allergist may
test you for allergy by doing skin tests, which involves pricking the skin or
injecting it with different allergens and observing for a reaction. A positive
reaction (a raised welt with redness around it) may indicate that you are
allergic to that allergen. Occasionally, your allergist may order a blood test
instead of the skin test to confirm the diagnosis of allergy.
What can I do to relieve house dust allergy
symptoms?
If you are tested and found to
be allergic to a component of house dust, specific avoidance measures can be
undertaken. Your allergist can give you expert advice on which avoidance
measures are right for you. The three basic treatments for dust allergy are:
- Avoidance, or limit exposure
- Medications
- Allergy shots (immunotherapy)
How do I avoid house dust?
Avoidance measures work best to relieve symptoms, but it's not possible to avoid
all exposure to all types of house dust. Some of these procedures are difficult,
and you may not need to do them all. Ask your allergist which ones will be most
helpful for your situation. If you're found to be allergic to furry pets, well,
there needs to be a family meeting to decide what is going to be done. In
general, finding another home for an allergenic pet followed by a thorough
housecleaning is the best solution for symptom control.
If you live in a dust mite area, you can not
eradicate them completely. First line steps to limit dust mite exposure focus on
the bedroom because, on average, people spend one-third of their lives in the
bedroom. Of all the rooms in the home, the bedroom often contains the most dust
mites. Special zip-up covers can seal dust mite particles inside your pillows
and mattresses. This will substantially limit your exposure to dust mite
particles, and should reduce your allergy symptoms. More extreme measures, such
as pulling up carpets and buying expensive dehumidifiers, should only be
undertaken in consultation with your allergist.
Copyright © 2002;
The American
College
of
Allergy
, Asthma & Immunology
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