Introduction

Sneezing is not always the symptom of a cold. Sometimes, it isan allergic reaction to something in the air. Experts estimatethat 35 million Americans suffer from upper respiratory symptomsthat are allergic reactions to airborne pollen. Pollen allergy,commonly called hay fever, is one of the most common chronicdiseases in the United States. Worldwide, airborne dust causesthe most problems for people with allergies. The respiratorysymptoms of asthma, which affects approximately 15 millionAmericans, are often provoked by airborne allergens (substancesthat cause an allergic reaction). 

Overall, allergic diseases are among the major causes ofillness and disability in the United States, affecting as many as40 to 50 million Americans. The National Institute of Allergy andInfectious Diseases, a component of the National Institutes ofHealth, conducts and supports research on allergic diseases. Thegoals of this research are to provide a better understanding ofthe causes of allergy, to improve the methods for diagnosing andtreating allergic reactions, and eventually to prevent allergies.This booklet summarizes what is known about the causes andsymptoms of allergic reactions to airborne allergens, how thesereactions are diagnosed and treated, and what medical researchersare doing to help people who suffer from these allergies.

***What is an allergy?***

An allergy is a specific immunologic reaction to a normallyharmless substance, one that does not bother most people. Peoplewho have allergies often are sensitive to more than onesubstance. Types of allergens that cause allergic reactionsinclude pollens, dust particles, mold spores, food, latex rubber,insect venom, or medicines. 

***Why are some people allergic tothese substances while others are not?***

Scientists think that people inherit a tendency to beallergic, meaning an increased likelihood of being allergic toone or more allergens, although they probably do not have aninherited tendency to be allergic to any specific allergens.Children are much more likely to develop allergies if theirparents have allergies, even if only one parent is allergic.Exposure to allergens at certain times when the body's defensesare lowered or weakened, such as after a viral infection orduring pregnancy, seems to contribute to the development ofallergies. 

***What is an allergic reaction?***

Normally, the immune system functions as the body's defenseagainst invading agents such as bacteria and viruses. In mostallergic reactions, however, the immune system is responding to afalse alarm. When an allergic person first comes into contactwith an allergen, the immune system treats the allergen as aninvader and mobilizes to attack. The immune system does this bygenerating large amounts of a type of antibody (adisease-fighting protein) called immunoglobin E, or IgE. Each IgEantibody is specific for one particular allergenic(allergy-producing) substance. In the case of pollen allergy, theantibody is specific for each type of pollen: one type ofantibody may be produced to react against oak pollen and anotheragainst ragweed pollen, for example. 

These IgE molecules are special because IgE is the only classof antibody that attaches tightly to the body's mast cells, whichare tissue cells, and to basophils, which are blood cells. Whenthe allergen next encounters its specific IgE, it attaches to theantibody like a key fitting into a lock, signaling the cell towhich the IgE is attached to release (and in some cases toproduce) powerful inflammatory chemicals like histamine,cytokines, and leukotrienes. These chemicals act on tissues invarious parts of the body, such as the respiratory system, andcause the symptoms of allergy.

Some people with allergy develop asthma. The symptoms ofasthma include coughing, wheezing, and shortness of breath due toa narrowing of the bronchial passages (airways) in the lungs, andto excess mucus production and inflammation. Asthma can bedisabling and sometimes can be fatal. If wheezing and shortnessof breath accompany allergy symptoms, it is a signal that thebronchial tubes also have become involved, indicating the needfor medical attention.

Symptoms of Allergies toAirborne 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 nasalpassages simply moves foreign particles to the throat, where theyare swallowed or coughed out. But something different happens toa person who is sensitive to airborne allergens.

As soon as the allergen lands on the mucous membranes liningthe inside of the nose, a chain reaction occurs that leads themast cells in these tissues to release histamine and otherchemicals. These powerful chemicals contract certain cells thatline some small blood vessels in the nose. This allows fluids toescape, which causes the nasal passages to swell, resulting innasal congestion. 

Histamine also can cause sneezing, itching, irritation, andexcess 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 allergicsymptoms. 

Pollen Allergy

Each spring, summer, and fall, tiny particles are releasedfrom trees, weeds, and grasses. These particles, known as pollen,hitch rides on currents of air. Although their mission is tofertilize parts of other plants, many never reach their targets.Instead, they enter human noses and throats, triggering a type ofseasonal allergic rhinitis called pollen allergy, which manypeople know as hay fever or rose fever (depending on the seasonin which the symptoms occur). Of all the things that can cause anallergy, pollen is one of the most widespread. Many of the foods,drugs, or animals that cause allergies can be avoided to a greatextent; even insects and household dust are escapable. Short ofstaying indoors when the pollen count is high--and even that maynot help--there is no easy way to evade windborne pollen.

People with pollen allergies often develop sensitivities toother troublemakers that are present all year, such as dustmites. For these allergy sufferers, the "sneezin'season" has no limit. Year-round airborne allergens causeperennial allergic rhinitis, as distinguished from seasonalallergic rhinitis. 

***What is pollen?***

Plants produce microscopic round or oval pollen grains toreproduce. In some species, the plant uses the pollen from itsown flowers to fertilize itself. Other types must becross-pollinated; that is, in order for fertilization to takeplace and seeds to form, pollen must be transferred from theflower of one plant to that of another plant of the same species.Insects do this job for certain flowering plants, while otherplants rely on wind transport. 

The types of pollen that most commonly cause allergicreactions are produced by the plain-looking plants (trees,grasses, and weeds) that do not have showy flowers. These plantsmanufacture small, light, dry pollen granules that arecustom-made for wind transport. Samples of ragweed pollen havebeen collected 400 miles out at sea and 2 miles high in the air.Because airborne pollen is carried for long distances, it doeslittle good to rid an area of an offending plant--the pollen candrift in from many miles away. In addition, most allergenicpollen comes from plants that produce it in huge quantities. Asingle ragweed plant can generate a million grains of pollen aday. 

The chemical makeup of pollen is the basic factor thatdetermines 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. Thechemical composition of pine pollen, however, appears to make itless 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 prolificproducers of allergenic pollen. Ragweed is the major culprit, butothers of importance are sagebrush, redroot pigweed, lamb'squarters, Russian thistle (tumbleweed), and English plantain. 

Grasses and trees, too, are important sources of allergenicpollens. Although more than 1,000 species of grass grow in NorthAmerica, only a few produce highly allergenic pollen. Theseinclude timothy grass, Kentucky bluegrass, Johnson grass, Bermudagrass, redtop grass, orchard grass, and sweet vernal grass. Treesthat 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 tocolorful or scented flowers like roses. In fact, only florists,gardeners, and others who have prolonged, close contact withflowers are likely to become sensitized to pollen from theseplants. Most people have little contact with the large, heavy,waxy pollen grains of many flowering plants because this type ofpollen is not carried by wind but by insects such as butterfliesand bees. 

***When do plants make pollen?***

One of the most obvious features of pollen allergy is itsseasonal nature--people experience it symptoms only when thepollen grains to which they are allergic are in the air. Eachplant has a pollinating period that is more or less the same fromyear to year. Exactly when a plant starts to pollinate seems todepend on the relative length of night and day--and therefore ongeographical location--rather than on the weather. (On the otherhand, weather conditions during pollination can affect the amountof pollen produced and distributed in a specific year.) Thus, thefarther north you go, the later the pollinating period and thelater the allergy season. 

A pollen count, which is familiar to many people from localweather reports, is a measure of how much pollen is in the air.This count represents the concentration of all the pollen (or ofone particular type, like ragweed) in the air in a certain areaat a specific time. It is expressed in grains of pollen persquare meter of air collected over 24 hours. Pollen counts tendto be highest early in the morning on warm, dry, breezy days andlowest during chilly, wet periods. Although a pollen count is anapproximate and fluctuating measure, it is useful as a generalguide for when it is advisable to stay indoors and avoid contactwith the pollen. 

Mold Allergy 

Along with pollens from trees, grasses, and weeds, molds arean important cause of seasonal allergic rhinitis. People allergicto molds may have symptoms from spring to late fall. The moldseason often peaks from July to late summer. Unlike pollens,molds may persist after the first killing frost. Some can grow atsubfreezing temperatures, but most become dormant. Snow coverlowers the outdoor mold count dramatically but does not killmolds. After the spring thaw, molds thrive on the vegetation thathas been killed by the winter cold. 

In the warmest areas of the United States, however, moldsthrive all year and can cause year-round (perennial) allergicproblems. In addition, molds growing indoors can cause perennialallergic rhinitis even in the coldest climates. 

***What is mold?***

There are thousands of types of molds and yeast, the twogroups of plants in the fungus family. Yeasts are single cellsthat divide to form clusters. Molds consist of many cells thatgrow as branching threads called hyphae. Although both groups canprobably cause allergic reactions, only a small number of moldsare widely recognized offenders. 

The seeds or reproductive particles of fungi are calledspores. They differ in size, shape, and color among species. Eachspore that germinates can give rise to new mold growth, which inturn 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 areso small, mold spores may evade the protective mechanisms of thenose and upper respiratory tract to reach the lungs.

In a small number of people, symptoms of mold allergy may bebrought on or worsened by eating certain foods, such as cheeses,processed with fungi. Occasionally, mushrooms, dried fruits, andfoods containing yeast, soy sauce, or vinegar will produceallergic symptoms. There is no known relationship, however,between a respiratory allergy to the mold *Penicillium* andan allergy to the drug penicillin, made from the mold. 

***Where do molds grow?***

Molds can be found wherever there is moisture, oxygen, and asource of the few other chemicals they need. In the fall theygrow on rotting logs and fallen leaves, especially in moist,shady areas. In gardens, they can be found in compost piles andon certain grasses and weeds. Some molds attach to grains such aswheat, oats, barley, and corn, making farms, grain bins, andsilos likely places to find mold. 

Hot spots of mold growth in the home include damp basementsand closets, bathrooms (especially shower stalls), places wherefresh food is stored, refrigerator drip trays, house plants, airconditioners, humidifiers, garbage pails, mattresses, upholsteredfurniture, and old foam rubber pillows. 

Bakeries, breweries, barns, dairies, and greenhouses arefavorite places for molds to grow. Loggers, mill workers,carpenters, furniture repairers, and upholsterers often work inmoldy environments. 

***Which molds are allergenic?***

Like pollens, mold spores are important airborne allergensonly if they are abundant, easily carried by air currents, andallergenic in their chemical makeup. Found almost everywhere,mold spores in some areas are so numerous they often outnumberthe pollens in the air. Fortunately, however, only a few dozendifferent types are significant allergens. 

In general, *Alternaria* and *Cladosporium(Hormodendrum)*are the molds most commonly found both indoorsand outdoors throughout the United States. *Aspergillus,Penicillium, Helminthosporium, Epicoccum, Fusarium, Mucor,Rhizopus*, and *Aureobasidium (Pullularia)*are alsocommon. 

***Are mold counts helpful?***

Similar to pollen counts, mold counts may suggest the typesand relative quantities of fungi present at a certain time andplace. For several reasons, however, these counts probably cannotbe used as a constant guide for daily activities. One reason isthat the number and types of spores actually present in the moldcount may have changed considerably in 24 hours because weatherand spore dispersal are directly related. Many of the commonallergenic molds are of the dry spore type--they release theirspores during dry, windy weather. Other fungi need high humidity,fog, or dew to release their spores. Although rain washes manylarger spores out of the air, it also causes some smaller sporesto be shot into the air. 

In addition to the effect of day-to-day weather changes onmold counts, spore populations may also differ between day andnight. Day favors dispersal by dry spore types and night favorswet spore types. 

***Are there other mold-relateddisorders?***

Fungi or microorganisms related to them may cause other healthproblems similar to allergic diseases. Some kinds of*Aspergillus* may cause several different illnesses, includingboth infections and allergy. These fungi may lodge in the airwaysor a distant part of the lung and grow until they form a compactsphere known as a "fungus ball." In people with lungdamage or serious underlying illnesses, *Aspergillus* maygrasp the opportunity to invade the lungs or the whole body. 

In some individuals, exposure to these fungi also can lead toasthma or to a lung disease resembling severe inflammatory asthmacalled allergic bronchopulmonary aspergillosis. This lattercondition, which occurs only in a minority of people with asthma,is characterized by wheezing, low-grade fever, and coughing up ofbrown-flecked masses or mucus plugs. Skin testing, blood tests,X-rays, and examination of the sputum for fungi can helpestablish the diagnosis. Corticosteroid drugs are usuallyeffective in treating this reaction; immunotherapy (allergyshots) is not helpful. 

Dust Mite Allergy

Dust mite allergy is an allergy to a microscopic organism thatlives in the dust that is found in all dwellings and workplaces.Dust mites are perhaps the most common cause of perennialallergic rhinitis. Dust mite allergy usually produces symptomssimilar to pollen allergy and also can produce symptoms ofasthma.

***What is house dust?***

Rather than a single substance, so-called house dust is avaried mixture of potentially allergenic materials. It maycontain 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 (especiallyin damp areas); food particles; bits of plants and insects; andother allergens peculiar to an individual home.

House dust also contains microscopic mites. These mites, whichlive in bedding, upholstered furniture, and carpets, thrive insummer and die in winter. In a warm, humid house, however, theycontinue to thrive even in the coldest months. The particles seenfloating in a shaft of sunlight include dead dust mites and theirwaste-products. These waste-products, which are proteins,actually provoke the allergic reaction. 

Waste products of cockroaches are also an important cause ofallergy symptoms from household allergens, particularly in someurban areas of the United States.

Animal Allergy

Household pets are the most common source of allergicreactions to animals. Many people think that pet allergy isprovoked by the fur of cats and dogs. But researchers have foundthat the major allergens are proteins secreted by oil glands inthe animals' skin and shed in dander as well as proteins in thesaliva, which sticks to the fur when the animal licks itself.Urine is also a source of allergy-causing proteins. When thesubstance carrying the proteins dries, the proteins can thenfloat into the air. Cats may be more likely than dogs to causeallergic reactions because they lick themselves more and may beheld more and spend more time in the house, close to humans.

Some rodents, such as guinea pigs and gerbils, have becomeincreasingly popular as household pets. They, too, can causeallergic reactions in some people, as can mice and rats. Urine isthe major source of allergens from these animals. 

Allergies to animals can take two years or more to develop andmay not subside until six months or more after ending contactwith the animal. Carpet and furniture are a reservoir for petallergens, and the allergens can remain in them for four to sixweeks. In addition, these allergens can stay in household air formonths after the animal has been removed. Therefore, it is wisefor people with an animal allergy to check with the landlord orprevious owner to find out if furry pets had lived previously onthe premises. 

Chemical Sensitivity

Some people report that they react to chemicals in theirenvironment and that these allergy-like reactions appear toresult from exposure to a wide variety of synthetic and naturalsubstances, such as those found in paints, carpeting, plastics,perfumes, cigarette smoke, and plants. Although the symptoms mayresemble some of the manifestations of allergies, sensitivity tochemicals does not represent a true allergic reaction involvingIgE and the release of histamine or other chemicals.

Diagnosing Allergic Diseases 

People with allergy symptoms, such as the runny nose ofallergic rhinitis, may at first suspect they have a cold--but the"cold" lingers on. It is important to see a doctorabout any respiratory illness that lasts longer than a week ortwo. When it appears that the symptoms are caused by an allergy,the patient should see a physician who understands the diagnosisand treatment of allergies. If the patient's medical historyindicates that the symptoms recur at the same time each year, thephysician will work under the theory that a seasonal allergen(like pollen) is involved. Properly trained specialists recognizethe patterns of potential allergens common during local seasonsand the association between these patterns and symptoms. Themedical history suggests which allergens are the likely culprits.The doctor also will examine the mucous membranes, which oftenappear swollen and pale or bluish in persons with allergicconditions.

***Skin Tests***

Doctors use skin tests to determine whether a patient has IgEantibodies in the skin that react to a specific allergen. Thedoctor will use diluted extracts from allergens such as dustmites, pollens, or molds commonly found in the local area. Theextract of each kind of allergen is injected under the patient'sskin or is applied to a tiny scratch or puncture made on thepatient's arm or back.

Skin tests are one way of measuring the level of IgE antibodyin a patient. With a positive reaction, a small, raised, reddenedarea (called a wheal) with a surrounding flush (called a flare)will appear at the test site. The size of the wheal can give thephysician an important diagnostic clue, but a positive reactiondoes not prove that a particular pollen is the cause of apatient's symptoms. Although such a reaction indicates that IgEantibody 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 costlyway to identify allergies in patients, some patients such asthose with widespread skin conditions like eczema should not betested using that method. There are other diagnostic tests thatuse a blood sample from the patient to detect levels of IgEantibody to a particular allergen. One such blood test is calledthe RAST (radioallergosorbent test), which can be performed wheneczema is present or if a patient has taken medications thatinterfere with skin testing. 

Treating People with AllergicDiseases 

Doctors use three general approaches to helping people withallergies: advise them on ways to avoid the allergen as much aspossible, prescribe medication to relieve symptoms, and give aseries of allergy shots. Although there is no cure for allergies,one of these strategies or a combination of them can providevarying degrees of relief from allergy symptoms.

***Avoidance***

Complete avoidance of allergenic pollen or mold means movingto a place where the offending substance does not grow and whereit is not present in the air. But even this extreme solution mayoffer only temporary relief since a person who is sensitive to aspecific pollen or mold may subsequently develop allergies to newallergens after repeated exposure. For example, people allergicto ragweed may leave their ragweed-ridden communities andrelocate to areas where ragweed does not grow, only to developallergies to other weeds or even to grasses or trees in their newsurroundings. Because relocating is not a reliable solution,allergy specialists do not encourage this approach. 

There are other ways to evade the offending pollen: remainingindoors in the morning, for example, when the outdoor pollenlevels are highest. Sunny, windy days can be especiallytroublesome. If individuals with pollen allergy must workoutdoors, they can wear face masks designed to filter pollen outof the air and keep it from reaching their nasal passages. Asanother approach, some people take their vacations at the heightof the expected pollinating period and choose a location wheresuch exposure would be minimal. The seashore, for example, may bean effective retreat for many with pollen allergies. 

Mold allergens can be difficult to avoid, but some steps canbe taken to at least reduce exposure to them. First, the allergysufferer should avoid those hot spots mentioned earlier wheremolds tend to be concentrated. The lawn should be mowed andleaves should be raked up, but someone other than the allergicperson should do these chores. If such work cannot be delegated,wearing a tightly fitting dust mask can greatly reduce exposureand resulting symptoms. Travel in the country, especially on dry,windy days or while crops are being harvested, should be avoidedas should walks through tall vegetation. A summer cabin closed upall winter is probably full of molds and should be aired out andcleaned before a mold-sensitive person stays there. 

Around the home, a dehumidifier will help dry out thebasement, but the water extracted from the air must be removedfrequently to prevent mold growth in the machine. 

Those with dust mite allergy should pay careful attention todust-proofing their bedrooms. The worst things to have in thebedroom are wall-to-wall carpets, venetian blinds, down-filledblankets, feather pillows, heating vents with forced hot air,dogs, cats, and closets full of clothing. Shades are preferredover venetian blinds because they do not trap dust. Curtains canbe used if they are washed periodically in hot water to kill thedust mites. Most important, bedding should be encased in azippered, plastic, airtight, and dust-proof cover. 

Although shag carpets are the worst type for the dustmite-sensitive person, all carpets trap dust and make dustcontrol impossible. In addition, vacuuming can contribute to theamount of dust, unless the vacuum is equipped with a specialhigh-efficiency particulate air (HEPA) filter. Wall-to-wallcarpets should be replaced with washable throw rugs overhardwood, tile, or linoleum floors. Rugs on concrete floorsencourage dust mite growth and should be avoided. 

Reducing the amount of dust mites in a home may require newcleaning techniques as well as some changes in furnishings toeliminate dust collectors. Water is often the secret to effectivedust removal. Washable items should be washed often using waterhotter then 130 (degrees) Fahrenheit. Lower temperatures will notkill dust mites. If the water temperature must be set at a lowervalue, items can be washed at a commercial establishment thatuses high wash temperatures. Dusting with a damp cloth or oiledmop 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 theanimal. There are, however, some suggestions that help lower thelevels of cat allergens in the air: bathe the cat weekly andbrush it more frequently (ideally, this should be done by someoneother than the allergic person), remove carpets and softfurnishings, and use a vacuum cleaner with a high-efficiencyfilter and a room air cleaner (see section below). Wearing a facemask while house and cat cleaning and keeping the cat out of thebedroom are other methods that allow many people to live morehappily with their pets. 

Irritants such as chemicals can worsen airborne allergysymptoms and should be avoided as much as possible. For example,during periods of high pollen levels, people with pollen allergyshould try to avoid unnecessary exposure to irritants such asinsect sprays, tobacco smoke, air pollution, and fresh tar orpaint. 

***Air conditioners and filters***

When possible, an allergic person should use air conditionersinside the home or in a car to help prevent pollen and moldallergens from entering. Various types of air-filtering devicesmade with fiberglass or electrically charged plates may helpreduce allergens produced in the home. These can be added to theheating and cooling systems. In addition, portable devices thatcan be used in individual rooms are especially helpful inreducing animal allergens. 

An allergy specialist can suggest which kind of filter is bestfor the home of a particular patient. Before buying a filteringdevice, the patient should rent one and use it in a closed room(the bedroom, for instance) for a month or two to see whetherallergy symptoms diminish. The airflow should be sufficient toexchange the air in the room five or six times per hour;therefore, the size and efficiency of the filtering device shouldbe determined in part by the size of the room. 

Persons with allergies should be wary of exaggerated claimsfor appliances that cannot really clean the air. Very small aircleaners cannot remove dust and pollen--and no air purifier canprevent viral or bacterial diseases such as influenza, pneumonia,or tuberculosis. Buyers of electrostatic precipitators shouldcompare the machine's ozone output with Federal standards. Ozonecan irritate the nose and airways of persons with allergies,especially those with asthma, and can increase the allergysymptoms. Other kinds of air filters such as HEPA filters do notrelease ozone into the air. HEPA filters, however, requireadequate air flow to force air through them.

***Medications***

For people who find they cannot adequately avoid airborneallergens, the symptoms often can be controlled with medications.Effective medications that can be prescribed by a physicianinclude antihistamines and topical nasal steroids--either ofwhich can be used alone or in combination. Many effectiveantihistamines and decongestants also are available without aprescription. 

*Antihistamines.*As thename indicates, an antihistamine counters the effects ofhistamine, which is released by the mast cells in the body'stissues and contributes to allergy symptoms. For many years,antihistamines have proven useful in relieving sneezing anditching in the nose, throat, and eyes, and in reducing nasalswelling and drainage. 

Many people who take antihistamines experience somedistressing side effects: drowsiness and loss of alertness andcoordination. In children, such reactions can be misinterpretedas behavior problems. During the last few years, however,antihistamines that cause fewer of these side effects have becomeavailable by prescription. These non-sedating antihistamines areas effective as other antihistamines in preventinghistamine-induced symptoms, but do so without causing sleepiness.Some of these non-sedating antihistamines, however, can haveserious side effects, particularly if they are taken with certainother drugs. A patient should always let the doctor know whatother medications he/she is taking.

*Topical nasal steroids.*Thismedication should not be confused with anabolic steroids, whichare sometimes used by athletes to enlarge muscle mass and canhave serious side effects. Topical nasal steroids areanti-inflammatory drugs that stop the allergic reaction. Inaddition to other beneficial actions, they reduce the number ofmast cells in the nose and reduce mucus secretion and nasalswelling. The combination of antihistamines and nasal steroids isa very effective way to treat allergic rhinitis, especially inpeople with moderate or severe allergic rhinitis. Althoughtopical nasal steroids can have side effects, they are safe whenused at recommended doses. Some of the newer agents are evensafer than older ones. 

*Cromolyn sodium.*Cromolynsodium for allergic rhinitis is a nasal spray that in some peoplehelps to prevent allergic reactions from starting. Whenadministered as a nasal spray, it can safely inhibit the releaseof chemicals like histamine from the mast cell. It has few sideeffects when used as directed, and significantly helps somepatients with allergies.

*Decongestants.*Sometimesre-establishing drainage of the nasal passages will help torelieve symptoms such as congestion, swelling, excess secretions,and discomfort in the sinus areas that can be caused by nasalallergies. (These sinus areas are hollow air spaces locatedwithin the bones of the skull surrounding the nose.) The doctormay recommend using oral or nasal decongestants to reducecongestion along with an antihistamine to control allerigicsymptoms. Over-the-counter and prescription decongestant nosedrops and sprays, however, should not be used for more than a fewdays. When used for longer periods, these drugs can lead to evenmore congestion and swelling of the nasal passages.

***Immunotherapy***

Immunotherapy, or a series of allergy shots, is the onlyavailable treatment that has a chance of reducing the allergysymptoms over a longer period of time. Patients receivesubcutaneous (under the skin) injections of increasingconcentrations of the allergen(s) to which they are sensitive.These injections reduce the amount of IgE antibodies in the bloodand cause the body to make a protective antibody called IgG. Manypatients with allergic rhinitis will have a significant reductionin their hay fever symptoms and in their need for medicationwithin 12 months of starting immunotherapy. Patients who benefitfrom immunotherapy may continue it for three years and thenconsider stopping. Although many patients are able to stop theinjections with good, long-term results, some do get worse afterimmunotherapy is stopped. As better allergens for immunotherapyare produced, this technique will become an even more effectivetreatment. 

Allergy Research 

The National Institute of Allergy and Infectious Diseases(NIAID) conducts and supports research on allergies focused onunderstanding what happens to the body during the allergicprocess--the sequence of events leading to the allergic responseand the factors responsible for allergic diseases. Thisunderstanding will lead to better methods of diagnosing,preventing, and treating allergies.

NIAID supports a network of Asthma, Allergic and ImmunologicDiseases Cooperative Research Centers throughout the UnitedStates. The centers encourage close coordination among scientistsstudying basic and clinical immunology, genetics, biochemistry,pharmacology, and environmental science. This interdisciplinaryapproach helps move research knowledge as quickly as possiblefrom research scientists to physicians and their allergypatients. 

Educating patients and health care workers is an importanttool in controlling allergic diseases. All of these researchcenters conduct and evaluate educational programs focused onmethods to control allergic diseases. 

Researchers participating in NIAID's National CooperativeInner-City Asthma Study are examining ways to prevent asthma inminority children in inner-city environments. Asthma, a majorcause of illness and hospitalizations among these children, isprovoked by a number of possible factors, including allergies toairborne substances. 

Although several factors provoke allergic responses,scientists know that heredity is a major influence on who willdevelop an allergy. Therefore, researchers are trying to identifyand describe the genes that make a person susceptible to allergicdiseases. 

Some studies are aimed at seeking better ways to diagnose andtreat people with allergic diseases and to better understand thefactors that regulate IgE production in order to reduce theallergic response in patients. Several research institutions arefocusing on ways to influence the cells that participate in theallergic response. 

Because researchers are becoming increasingly aware of therole of environmental factors in allergies, they are evaluatingways to control environmental exposures to allergens andpollutants to prevent allergic disease.

These studies offer the promise of improving treatment andcontrol of allergic diseases and the hope that one day allergicdiseases will be preventable as well. 

Information Resources

***for more information on allergicdiseases:***

**American Academy of Allergy, Asthmaand Immunology**611 East Wells StreetMilwaukee, WI 532021-800-822-ASMAhttp://www.aaaai.org

**Asthma and Allergy Foundation ofAmerica**1125 15th Street, N.W., Suite 502Washington, DC 200051-800-7-ASTHMAhttp://www.aafa.org

**Allergy and Asthma Network/Mothers ofAsthmatics, Inc.**3554 Chain Bridge Road, Suite 200Fairfax, VA 220301-800-878-4403http://www.podi.com/health/aanma

***for more information onair-cleaning devices:***

**Environmental Protection Agency**Public Information Service401 M Street, S.W.Washington, DC 204601-800-438-4318http://www.epa.gov

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