Pollen allergy, commonly called hay fever, is one of the most
common chronic diseases in the United States. Worldwide, airborne dust causes the most
problems for people with allergies. The respiratory symptoms of asthma, which affects
approximately 15 million Americans, are often provoked by airborne allergens (substances
that cause an allergic reaction).
Overall, allergic diseases are among the major causes of illness
and disability in the United States, affecting as many as 40 to 50 million Americans. The
National Institute of Allergy and Infectious Diseases, a component of the National
Institutes of Health, conducts and supports research on allergic diseases. The goals of
this research are to provide a better understanding of the causes of allergy, to improve
the methods for diagnosing and treating allergic reactions, and eventually to prevent
allergies. This booklet summarizes what is known about the causes and symptoms of allergic
reactions to airborne allergens, how these reactions are diagnosed and treated, and what
medical researchers are doing to help people who suffer from these allergies.
What is an allergy?
An allergy is a specific immunologic reaction to a normally harmless substance,
one that does not bother most people. People who have allergies often are sensitive to
more than one substance. Types of allergens that cause allergic reactions include pollens,
dust particles, mold spores, food, latex rubber, insect venom, or medicines.
Why are some people allergic to these substances
while others are not?
Scientists think that people inherit a tendency to be
allergic, meaning an increased likelihood of being allergic to one or more allergens,
although they probably do not have an inherited tendency to be allergic to any specific
allergens. Children are much more likely to develop allergies if their parents have
allergies, even if only one parent is allergic. Exposure to allergens at certain times
when the body's defenses are lowered or weakened, such as after a viral infection or
during pregnancy, seems to contribute to the development of allergies.
What is an allergic reaction?
Normally, the immune system functions as the body's defense
against invading agents such as bacteria and viruses. In most allergic reactions, however,
the immune system is responding to a false alarm. When an allergic person first comes into
contact with an allergen, the immune system treats the allergen as an invader and
mobilizes to attack. The immune system does this by generating large amounts of a type of
antibody (a disease-fighting protein) called immunoglobin E, or IgE. Each IgE antibody is
specific for one particular allergenic (allergy-producing) substance. In the case of
pollen allergy, the antibody is specific for each type of pollen: one type of antibody may
be produced to react against oak pollen and another against ragweed pollen, for example.
These IgE molecules are special because IgE is the only class
of antibody that attaches tightly to the body's mast cells, which are tissue cells, and to
basophils, which are blood cells. When the allergen next encounters its specific IgE, it
attaches to the antibody like a key fitting into a lock, signaling the cell to which the
IgE is attached to release (and in some cases to produce) powerful inflammatory chemicals
like histamine, cytokines, and leukotrienes. These chemicals act on tissues in various
parts of the body, such as the respiratory system, and cause the symptoms of allergy.
Some people with allergy develop asthma. The symptoms of
asthma include coughing, wheezing, and shortness of breath due to a narrowing of the
bronchial passages (airways) in the lungs, and to excess mucus production and
inflammation. Asthma can be disabling and sometimes can be fatal. If wheezing and
shortness of breath accompany allergy symptoms, it is a signal that the bronchial tubes
also have become involved, indicating the need for medical attention.
Symptoms of Allergies to Airborne Substances
The signs and symptoms are familiar to many:
- Sneezing often accompanied by a runny or clogged nose
- Coughing and postnasal drip
- Itching eyes, nose, and throat
- Allergic shiners (dark circles under the eyes caused by
increased blood flow near the sinuses)
- The "allergic salute" (in a child, persistent upward
rubbing of the nose that causes a crease mark on the nose)
- Watering eyes
- Conjunctivitis (an inflammation of the membrane that lines the
eyelids, causing red-rimmed, swollen eyes, and crusting of the eyelids)
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.
Pollen Allergy
Each spring, summer, and fall, tiny particles
are released from trees, weeds, and grasses. These particles, known as pollen, hitch rides
on currents of air. Although their mission is to fertilize parts of other plants, many
never reach their targets. Instead, they enter human noses and throats, triggering a type
of seasonal allergic rhinitis called pollen allergy, which many people know as hay fever
or rose fever (depending on the season in which the symptoms occur). Of all the things
that can cause an allergy, pollen is one of the most widespread. Many of the foods, drugs,
or animals that cause allergies can be avoided to a great extent; even insects and
household dust are escapable. Short of staying indoors when the pollen count is high --
and even that may not help -- there is no easy way to evade windburn pollen.
People with pollen allergies often develop
sensitivities to other troublemakers that are present all year, such as dust mites. For
these allergy sufferers, the "sneezin' season" has no limit. Year-round airborne
allergens cause perennial allergic rhinitis, as distinguished from seasonal allergic
rhinitis.
What is pollen?
Plants produce microscopic round or oval
pollen grains to reproduce. In some species, the plant uses the pollen from its own
flowers to fertilize itself. Other types must be cross-pollinated; that is, in order for
fertilization to take place and seeds to form, pollen must be transferred from the flower
of one plant to that of another plant of the same species. Insects do this job for certain
flowering plants, while other plants rely on wind transport.
The types of pollen that most commonly cause
allergic reactions are produced by the plain-looking plants (trees, grasses, and weeds)
that do not have showy flowers. These plants manufacture small, light, dry pollen granules
that are custom-made for wind transport. Samples of ragweed pollen have been collected 400
miles out at sea and 2 miles high in the air. Because airborne pollen is carried for long
distances, it does little good to rid an area of an offending plant -- the pollen can
drift in from many miles away. In addition, most allergenic pollen comes from plants that
produce it in huge quantities. A single ragweed plant can generate a million grains of
pollen a day.
The chemical makeup of pollen is the basic
factor that determines whether it is likely to cause hay fever. For example, pine tree
pollen is produced in large amounts by a common tree, which would make it a good candidate
for causing allergy. The chemical composition of pine pollen, however, appears to make it
less allergenic than other types. Because pine pollen is heavy, it tends to fall straight
down and does not scatter. Therefore, it rarely reaches human noses.
Among North American plants, weeds are the
most prolific producers of allergenic pollen. Ragweed is the major culprit, but others of
importance are sagebrush, redroot pigweed, lamb's quarters, Russian thistle (tumbleweed),
and English plantain.
Grasses and trees, too, are important sources
of allergenic pollens. Although more than 1,000 species of grass grow in North America,
only a few produce highly allergenic pollen. These include timothy grass, Kentucky
bluegrass, Johnson grass, Bermuda grass, redtop grass, orchard grass, and sweet vernal
grass. Trees that produce allergenic pollen include oak, ash, elm, hickory, pecan, box
elder, and mountain cedar.
It is common to hear people say that they are
allergic to colorful or scented flowers like roses. In fact, only florists, gardeners, and
others who have prolonged, close contact with flowers are likely to become sensitized to
pollen from these plants. Most people have little contact with the large, heavy, waxy
pollen grains of many flowering plants because this type of pollen is not carried by wind
but by insects such as butterflies and bees.
When do plants make pollen?
One of the most obvious features of pollen
allergy is its seasonal nature -- people experience it symptoms only when the pollen
grains to which they are allergic are in the air. Each plant has a pollinating period that
is more or less the same from year to year. Exactly when a plant starts to pollinate seems
to depend on the relative length of night and day -- and therefore on geographical
location -- rather than on the weather. (On the other hand, weather conditions during
pollination can affect the amount of pollen produced and distributed in a specific year.)
Thus, the farther north you go, the later the pollinating period and the later the allergy
season.
A pollen count, which is familiar to many
people from local weather reports, is a measure of how much pollen is in the air. This
count represents the concentration of all the pollen (or of one particular type, like
ragweed) in the air in a certain area at a specific time. It is expressed in grains of
pollen per square meter of air collected over 24 hours. Pollen counts tend to be highest
early in the morning on warm, dry, breezy days and lowest during chilly, wet periods.
Although a pollen count is an approximate and fluctuating measure, it is useful as a
general guide for when it is advisable to stay indoors and avoid contact with the pollen.
Mold Allergy
Along with pollens from trees, grasses, and
weeds, molds are an important cause of seasonal allergic rhinitis. People allergic to
molds may have symptoms from spring to late fall. The mold season often peaks from July to
late summer. Unlike pollens, molds may persist after the first killing frost. Some can
grow at subfreezing temperatures, but most become dormant. Snow cover lowers the outdoor
mold count dramatically but does not kill molds. After the spring thaw, molds thrive on
the vegetation that has been killed by the winter cold.
In the warmest areas of the United States,
however, molds thrive all year and can cause year-round (perennial) allergic problems. In
addition, molds growing indoors can cause perennial allergic rhinitis even in the coldest
climates.
What is mold?
There are thousands of types of molds and
yeast, the two groups of plants in the fungus family. Yeasts are single cells that divide
to form clusters. Molds consist of many cells that grow as branching threads called
hyphae. Although both groups can probably cause allergic reactions, only a small number of
molds are widely recognized offenders.
The seeds or reproductive particles of fungi
are called spores. They differ in size, shape, and color among species. Each spore that
germinates can give rise to new mold growth, which in turn can produce millions of spores.
What is mold allergy?
When inhaled, microscopic fungal spores or,
sometimes, fragments of fungi may cause allergic rhinitis. Because they are so small, mold
spores may evade the protective mechanisms of the nose and upper respiratory tract to
reach the lungs.
In a small number of people, symptoms of mold
allergy may be brought on or worsened by eating certain foods, such as cheeses, processed
with fungi. Occasionally, mushrooms, dried fruits, and foods containing yeast, soy sauce,
or vinegar will produce allergic symptoms. There is no known relationship, however,
between a respiratory allergy to the mold Penicillium and an allergy to the drug
penicillin, made from the mold.
Where do molds grow?
Molds can be found wherever there is
moisture, oxygen, and a source of the few other chemicals they need. In the fall they grow
on rotting logs and fallen leaves, especially in moist, shady areas. In gardens, they can
be found in compost piles and on certain grasses and weeds. Some molds attach to grains
such as wheat, oats, barley, and corn, making farms, grain bins, and silos likely places
to find mold.
Hot spots of mold growth in the home include
damp basements and closets, bathrooms (especially shower stalls), places where fresh food
is stored, refrigerator drip trays, house plants, air conditioners, humidifiers, garbage
pails, mattresses, upholstered furniture, and old foam rubber pillows.
Bakeries, breweries, barns, dairies, and
greenhouses are favorite places for molds to grow. Loggers, mill workers, carpenters,
furniture repairers, and upholsterers often work in moldy environments.
Which molds are allergenic?
Like pollens, mold spores are important
airborne allergens only if they are abundant, easily carried by air currents, and
allergenic in their chemical makeup. Found almost everywhere, mold spores in some areas
are so numerous they often outnumber the pollens in the air. Fortunately, however, only a
few dozen different types are significant allergens.
In general, Alternaria and Cladosporium
(Hormodendrum) are the molds most commonly found both indoors and outdoors throughout the
United States. Aspergillus, Penicillium, Helminthosporium, Epicoccum, Fusarium, Mucor,
Rhizopus, and Aureobasidium (Pullularia) are also common.
Are mold counts helpful?
Similar to pollen counts, mold counts may
suggest the types and relative quantities of fungi present at a certain time and place.
For several reasons, however, these counts probably cannot be used as a constant guide for
daily activities. One reason is that the number and types of spores actually present in
the mold count may have changed considerably in 24 hours because weather and spore
dispersal are directly related. Many of the common allergenic molds are of the dry spore
type -- they release their spores during dry, windy weather. Other fungi need high
humidity, fog, or dew to release their spores. Although rain washes many larger spores out
of the air, it also causes some smaller spores to be shot into the air.
In addition to the effect of day-to-day
weather changes on mold counts, spore populations may also differ between day and night.
Day favors dispersal by dry spore types and night favors wet spore types.
Are there other mold-related disorders?
Fungi or microorganisms related to them may
cause other health problems similar to allergic diseases. Some kinds of Aspergillus may
cause several different illnesses, including both infections and allergy. These fungi may
lodge in the airways or a distant part of the lung and grow until they form a compact
sphere known as a "fungus ball." In people with lung damage or serious
underlying illnesses, Aspergillus may grasp the opportunity to invade the lungs or the
whole body.
In some individuals, exposure to these fungi
also can lead to asthma or to a lung disease resembling severe inflammatory asthma called
allergic bronchopulmonary aspergillosis. This latter condition, which occurs only in a
minority of people with asthma, is characterized by wheezing, low-grade fever, and
coughing up of brown-flecked masses or mucus plugs. Skin testing, blood tests, X-rays, and
examination of the sputum for fungi can help establish the diagnosis. Corticosteroid drugs
are usually effective in treating this reaction; immunotherapy (allergy shots) is not
helpful.
Dust Mite Allergy
Dust mite allergy is an allergy to a
microscopic organism that lives in the dust that is found in all dwellings and workplaces.
Dust mites are perhaps the most common cause of perennial allergic rhinitis. Dust mite
allergy usually produces symptoms similar to pollen allergy and also can produce symptoms
of asthma.
What is house dust?
Rather than a single substance, so-called
house dust is a varied mixture of potentially allergenic materials. It may contain fibers
from different types of fabrics; cotton lint, feathers, and other stuffing materials;
dander from cats, dogs, and other animals; bacteria; mold and fungus spores (especially in
damp areas); food particles; bits of plants and insects; and other allergens peculiar to
an individual home.
House dust also contains microscopic mites.
These mites, which live in bedding, upholstered furniture, and carpets, thrive in summer
and die in winter. In a warm, humid house, however, they continue to thrive even in the
coldest months. The particles seen floating in a shaft of sunlight include dead dust mites
and their waste-products. These waste-products, which are proteins, actually provoke the
allergic reaction.
Waste products of cockroaches are also an
important cause of allergy symptoms from household allergens, particularly in some urban
areas of the United States.
Animal Allergy
Household pets are the most common source of
allergic reactions to animals. Many people think that pet allergy is provoked by the fur
of cats and dogs. But researchers have found that the major allergens are proteins
secreted by oil glands in the animals' skin and shed in dander as well as proteins in the
saliva, which sticks to the fur when the animal licks itself. Urine is also a source of
allergy-causing proteins. When the substance carrying the proteins dries, the proteins can
then float into the air. Cats may be more likely than dogs to cause allergic reactions
because they lick themselves more and may be held more and spend more time in the house,
close to humans.
Some rodents, such as guinea pigs and
gerbils, have become increasingly popular as household pets. They, too, can cause allergic
reactions in some people, as can mice and rats. Urine is the major source of allergens
from these animals.
Allergies to animals can take two years or
more to develop and may not subside until six months or more after ending contact with the
animal. Carpet and furniture are a reservoir for pet allergens, and the allergens can
remain in them for four to six weeks. In addition, these allergens can stay in household
air for months after the animal has been removed. Therefore, it is wise for people with an
animal allergy to check with the landlord or previous owner to find out if furry pets had
lived previously on the premises.
Chemical Sensitivity
Some people report that they react to
chemicals in their environment and that these allergy-like reactions appear to result from
exposure to a wide variety of synthetic and natural substances, such as those found in
paints, carpeting, plastics, perfumes, cigarette smoke, and plants. Although the symptoms
may resemble some of the manifestations of allergies, sensitivity to chemicals does not
represent a true allergic reaction involving IgE and the release of histamine or other
chemicals.
Diagnosing Allergic Diseases
People with allergy symptoms, such as the
runny nose of allergic rhinitis, may at first suspect they have a cold -- but the
"cold" lingers on. It is important to see a doctor about any respiratory illness
that lasts longer than a week or two. When it appears that the symptoms are caused by an
allergy, the patient should see a physician who understands the diagnosis and treatment of
allergies. If the patient's medical history indicates that the symptoms recur at the same
time each year, the physician will work under the theory that a seasonal allergen (like
pollen) is involved. Properly trained specialists recognize the patterns of potential
allergens common during local seasons and the association between these patterns and
symptoms. The medical history suggests which allergens are the likely culprits. The doctor
also will examine the mucous membranes, which often appear swollen and pale or bluish in
persons with allergic conditions.
Skin Tests
Doctors use skin tests to determine whether a
patient has IgE antibodies in the skin that react to a specific allergen. The doctor will
use diluted extracts from allergens such as dust mites, pollens, or molds commonly found
in the local area. The extract of each kind of allergen is injected under the patient's
skin or is applied to a tiny scratch or puncture made on the patient's arm or back.
Skin tests are one way of measuring the level
of IgE antibody in a patient. With a positive reaction, a small, raised, reddened area
(called a wheal) with a surrounding flush (called a flare) will appear at the test site.
The size of the wheal can give the physician an important diagnostic clue, but a positive
reaction does not prove that a particular pollen is the cause of a patient's symptoms.
Although such a reaction indicates that IgE antibody to a specific allergen is present in
the skin, respiratory symptoms do not necessarily result.
Blood Tests
Although skin testing is the most sensitive
and least costly way to identify allergies in patients, some patients such as those with
widespread skin conditions like eczema should not be tested using that method. There are
other diagnostic tests that use a blood sample from the patient to detect levels of IgE
antibody to a particular allergen. One such blood test is called the RAST
(radioallergosorbent test), which can be performed when eczema is present or if a patient
has taken medications that interfere with skin testing.
Treating People with Allergic Diseases
Doctors use three general approaches to
helping people with allergies: advise them on ways to avoid the allergen as much as
possible, prescribe medication to relieve symptoms, and give a series of allergy shots.
Although there is no cure for allergies, one of these strategies or a combination of them
can provide varying degrees of relief from allergy symptoms.
Avoidance
Complete avoidance of allergenic pollen or
mold means moving to a place where the offending substance does not grow and where it is
not present in the air. But even this extreme solution may offer only temporary relief
since a person who is sensitive to a specific pollen or mold may subsequently develop
allergies to new allergens after repeated exposure. For example, people allergic to
ragweed may leave their ragweed-ridden communities and relocate to areas where ragweed
does not grow, only to develop allergies to other weeds or even to grasses or trees in
their new surroundings. Because relocating is not a reliable solution, allergy specialists
do not encourage this approach.
There are other ways to evade the offending
pollen: remaining indoors in the morning, for example, when the outdoor pollen levels are
highest. Sunny, windy days can be especially troublesome. If individuals with pollen
allergy must work outdoors, they can wear face masks designed to filter pollen out of the
air and keep it from reaching their nasal passages. As another approach, some people take
their vacations at the height of the expected pollinating period and choose a location
where such exposure would be minimal. The seashore, for example, may be an effective
retreat for many with pollen allergies.
Mold allergens can be difficult to avoid, but
some steps can be taken to at least reduce exposure to them. First, the allergy sufferer
should avoid those hot spots mentioned earlier where molds tend to be concentrated. The
lawn should be mowed and leaves should be raked up, but someone other than the allergic
person should do these chores. If such work cannot be delegated, wearing a tightly fitting
dust mask can greatly reduce exposure and resulting symptoms. Travel in the country,
especially on dry, windy days or while crops are being harvested, should be avoided as
should walks through tall vegetation. A summer cabin closed up all winter is probably full
of molds and should be aired out and cleaned before a mold-sensitive person stays there.
Around the home, a dehumidifier will help dry
out the basement, but the water extracted from the air must be removed frequently to
prevent mold growth in the machine.
Those with dust mite allergy should pay
careful attention to dust-proofing their bedrooms. The worst things to have in the bedroom
are wall-to-wall carpets, venetian blinds, down-filled blankets, feather pillows, heating
vents with forced hot air, dogs, cats, and closets full of clothing. Shades are preferred
over venetian blinds because they do not trap dust. Curtains can be used if they are
washed periodically in hot water to kill the dust mites. Most important, bedding should be
encased in a zippered, plastic, airtight, and dust-proof cover.
Although shag carpets are the worst type for
the dust mite-sensitive person, all carpets trap dust and make dust control impossible. In
addition, vacuuming can contribute to the amount of dust, unless the vacuum is equipped
with a special high-efficiency particulate air (HEPA) filter. Wall-to-wall carpets should
be replaced with washable throw rugs over hardwood, tile, or linoleum floors. Rugs on
concrete floors encourage dust mite growth and should be avoided.
Reducing the amount of dust mites in a home
may require new cleaning techniques as well as some changes in furnishings to eliminate
dust collectors. Water is often the secret to effective dust removal. Washable items
should be washed often using water hotter then 130 degrees Fahrenheit. Lower temperatures
will not kill dust mites. If the water temperature must be set at a lower value, items can
be washed at a commercial establishment that uses high wash temperatures. Dusting with a
damp cloth or oiled mop should be done frequently.
The best way for a person allergic to pets,
especially cats, to avoid allergic reactions is to find another home for the animal. There
are, however, some suggestions that help lower the levels of cat allergens in the air:
bathe the cat weekly and brush it more frequently (ideally, this should be done by someone
other than the allergic person), remove carpets and soft furnishings, and use a vacuum
cleaner with a high-efficiency filter and a room air cleaner (see section below). Wearing
a face mask while house and cat cleaning and keeping the cat out of the bedroom are other
methods that allow many people to live more happily with their pets.
Irritants such as chemicals can worsen
airborne allergy symptoms and should be avoided as much as possible. For example, during
periods of high pollen levels, people with pollen allergy should try to avoid unnecessary
exposure to irritants such as insect sprays, tobacco smoke, air pollution, and fresh tar
or paint.
Air Conditioners and Filters
When possible, an allergic person should use
air conditioners inside the home or in a car to help prevent pollen and mold allergens
from entering. Various types of air-filtering devices made with fiberglass or electrically
charged plates may help reduce allergens produced in the home. These can be added to the
heating and cooling systems. In addition, portable devices that can be used in individual
rooms are especially helpful in reducing animal allergens.
An allergy specialist can suggest which kind
of filter is best for the home of a particular patient. The airflow should be sufficient
to exchange the air in the room five or six times per hour; therefore, the size and
efficiency of the filtering device should be determined in part by the size of the room.
Very small air cleaners cannot remove dust
and pollen. Buyers of electrostatic precipitators should compare the machine's ozone
output with Federal standards. Ozone can irritate the nose and airways of persons with
allergies, especially those with asthma, and can increase the allergy symptoms. Other
kinds of air filters such as HEPA filters do not release ozone into the air. HEPA filters
require adequate air flow to force air through them.
Medications
For people who find they cannot adequately
avoid airborne allergens, the symptoms often can be controlled with medications. Effective
medications that can be prescribed by a physician include antihistamines and topical nasal
steroids -- either of which can be used alone or in combination. Many effective
antihistamines and decongestants also are available without a prescription.
Antihistamines. As the name indicates, an
antihistamine counters the effects of histamine, which is released by the mast cells in
the body's tissues and contributes to allergy symptoms. For many years, antihistamines
have proven useful in relieving sneezing and itching in the nose, throat, and eyes, and in
reducing nasal swelling and drainage.
Many people who take antihistamines
experience some distressing side effects: drowsiness and loss of alertness and
coordination. In children, such reactions can be misinterpreted as behavior problems.
During the last few years, however, antihistamines that cause fewer of these side effects
have become available by prescription. These non-sedating antihistamines are as effective
as other antihistamines in preventing histamine-induced symptoms, but do so without
causing sleepiness. Some of these non-sedating antihistamines, however, can have serious
side effects, particularly if they are taken with certain other drugs. A patient should
always let the doctor know what other medications he/she is taking.
Topical nasal steroids. This medication
should not be confused with anabolic steroids, which are sometimes used by athletes to
enlarge muscle mass and can have serious side effects. Topical nasal steroids are
anti-inflammatory drugs that stop the allergic reaction. In addition to other beneficial
actions, they reduce the number of mast cells in the nose and reduce mucus secretion and
nasal swelling. The combination of antihistamines and nasal steroids is a very effective
way to treat allergic rhinitis, especially in people with moderate or severe allergic
rhinitis. Although topical nasal steroids can have side effects, they are safe when used
at recommended doses. Some of the newer agents are even safer than older ones.
Cromolyn sodium. Cromolyn sodium for allergic
rhinitis is a nasal spray that in some people helps to prevent allergic reactions from
starting. When administered as a nasal spray, it can safely inhibit the release of
chemicals like histamine from the mast cell. It has few side effects when used as
directed, and significantly helps some patients with allergies.
Decongestants. Sometimes re-establishing
drainage of the nasal passages will help to relieve symptoms such as congestion, swelling,
excess secretions, and discomfort in the sinus areas that can be caused by nasal
allergies. (These sinus areas are hollow air spaces located within the bones of the skull
surrounding the nose.) The doctor may recommend using oral or nasal decongestants to
reduce congestion along with an antihistamine to control allergic symptoms.
Over-the-counter and prescription decongestant nose drops and sprays, however, should not
be used for more than a few days. When used for longer periods, these drugs can lead to
even more congestion and swelling of the nasal passages.
Immunotherapy
Immunotherapy, or a series of allergy shots,
is the only available treatment that has a chance of reducing the allergy symptoms over a
longer period of time. Patients receive subcutaneous (under the skin) injections of
increasing concentrations of the allergen(s) to which they are sensitive. These injections
reduce the amount of IgE antibodies in the blood and cause the body to make a protective
antibody called IgG. Many patients with allergic rhinitis will have a significant
reduction in their hay fever symptoms and in their need for medication within 12 months of
starting immunotherapy. Patients who benefit from immunotherapy may continue it for three
years and then consider stopping. Although many patients are able to stop the injections
with good, long-term results, some do get worse after immunotherapy is stopped. As better
allergens for immunotherapy are produced, this technique will become an even more
effective treatment.
Allergy Research
The National Institute of Allergy and
Infectious Diseases (NIAID) conducts and supports research on allergies focused on
understanding what happens to the body during the allergic process -- the sequence of
events leading to the allergic response and the factors responsible for allergic diseases.
This understanding will lead to better methods of diagnosing, preventing, and treating
allergies.
NIAID supports a network of Asthma, Allergic
and Immunologic Diseases Cooperative Research Centers throughout the United States. The
centers encourage close coordination among scientists studying basic and clinical
immunology, genetics, biochemistry, pharmacology, and environmental science. This
interdisciplinary approach helps move research knowledge as quickly as possible from
research scientists to physicians and their allergy patients.
Educating patients and health care
workers is an important tool in controlling allergic diseases. All of these research
centers conduct and evaluate educational programs focused on methods to control allergic
diseases.
Researchers participating in NIAID's
National Cooperative Inner-City Asthma Study are examining ways to prevent asthma in
minority children in inner-city environments. Asthma, a major cause of illness and
hospitalizations among these children, is provoked by a number of possible factors,
including allergies to airborne substances.
Although several factors provoke allergic
responses, scientists know that heredity is a major influence on who will develop an
allergy. Therefore, researchers are trying to identify and describe the genes that make a
person susceptible to allergic diseases.
Some studies are aimed at seeking
better ways to diagnose and treat people with allergic diseases and to better understand
the factors that regulate IgE production in order to reduce the allergic response in
patients. Several research institutions are focusing on ways to influence the cells that
participate in the allergic response.
Because researchers are becoming
increasingly aware of the role of environmental factors in allergies, they are evaluating
ways to control environmental exposures to allergens and pollutants to prevent allergic
disease.
These studies offer the promise of
improving treatment and control of allergic diseases and the hope that one day allergic
diseases will be preventable as well. |
