Asthma: Calming the AirwaysPage 7 of 11

5. Environmental Factors in Asthma

Environmental triggers, irritants, allergens, occupational exposures, and other causal factors must be considered in clients with asthma symptoms.

Triggers, Irritants, and Allergens

Successful long-term control of asthma requires identifying environmental triggers, allergens, and irritants that increase symptoms or precipitate exacerbations. Because these factors are at least potentially modifiable, it is important to either remove or minimize them to reduce overall risk.

Education and abatement are essential prerequisites for convincing clients about the need for specific allergen avoidance. It is only possible to convince clients to undertake the abatement measures when they know what their triggers are.

Determination of sensitivity to a specific allergen is usually not possible through the client’s medical history alone, but requires testing. Current recommendations for avoidance measures are allergen-specific and clients should be tested for sensitivity only to allergens they may be exposed to. Skin or in vitro tests educate clients about the role of allergens in their disease and are reliable in determining the presence of specific allergens. These tests, however, do not determine whether the specific immunoglobulin is responsible for the client’s symptoms.

Inhaled Allergens

The most important allergens for children and adults appear to be those that are inhaled. Exposure to inhaled allergens increases airway inflammation and symptoms. Substantially reducing such exposure may significantly reduce inflammation, symptoms, and need for medication. Demonstrating a patient’s relevant sensitivity to inhalant allergens will enable the clinician to recommend specific environmental controls to reduce exposures. It will also help the patient understand the pathogenesis of asthma and the value of allergen avoidance (NIH, NHLBI, 2007).

Dust Mites

House dust mites are universal in areas of high humidity (most areas of the United States) but are usually not present at high altitudes or in arid areas unless moisture is added to the indoor air via swamp coolers and other moisture sources. Mites depend on atmospheric moisture and human dander for survival. High levels of mites can be found in dust from mattresses, pillows, carpets, upholstered furniture, bed covers, clothes, and soft toys. The client’s bed is the most important source of dust mites to control. Washing bedding is advised, preferably in hot water, but cold water, detergent, and bleach can also be effective.

Chemical agents are available for killing mites and denaturing the antigen; however, the effects are not dramatic and do not appear to be sustained for long periods. Use of these agents in homes of persons who have asthma and are sensitive to house dust mites should not be recommended routinely. Vacuuming removes mite allergen from carpets, but is inefficient at removing live mites. Eliminating conditions in which mites flourish such as areas with abundant densely layered fabric or carpeting and substituting them for surfaces that are easily cleaned is effective, but may not be practical or possible.

Pet Dander

Warm-blooded animals—including pets and rodents—produce dander, urine, feces, and saliva that can cause allergic reactions. Successful controlled trials of high animal dander concentrations and abatement have been reported for schools and homes in which no animal is present (Dilley & Phipatanakul, 2017) but where significant dander counts have been recorded.

High-efficiency particulate air (HEPA) cleaners reduce airborne particles in homes with dogs, but this does not hold true for cat dander, which has greater allergenic properties and is far more sensitizing. Preventing pets from having access to the bedroom—and possibly the living room—may reduce the total allergen load inhaled although by itself this measure may not be enough. Weekly washing of the pet will remove dander and dried saliva that will otherwise accumulate in the house; however, the role of washing in allergen avoidance is not established once an individual has been sensitized (Dilley & Phipatanakul, 2017).


Cockroach sensitivity is common among clients who have asthma, and those who live in inner cities suffer disproportionately. In a study of asthma in an inner-city area, asthma severity increased with increasing levels of cockroach antigen in the bedrooms of children who were sensitized.

Avoidance of conditions in which cockroaches are known to flourish is effective in reducing populations, but this can be difficult in poorly maintained and densely crowded living quarters in urban settings. Clients and caretakers should not leave food or garbage exposed. Poison baits, boric acid, and traps are preferred to other chemical agents such as sprays or fumigant bombs, because the latter can be irritating when inhaled by persons who have asthma. If volatile chemical agents are used, or a building is commercially fumigated, the home should be well ventilated after the chemicals have been dispersed, and the person who has asthma should not return to the home until the odor has dissipated. Care should be taken that young children do not have access to cockroach baits and poisons (Dilley & Phipatanakul, 2017).

Indoor Fungi (Molds)

Indoor fungi are particularly prominent in humid environments and homes that have problems with dampness. Children who live in homes with moisture problems have increased respiratory symptoms (NIH, NHLBI, 2007), but the relative contribution of fungi, house dust mites, or irritants is variable, making it difficult to guarantee improvement using a “one size fits all” approach. Because an association between indoor fungi and respiratory and allergic disease is suggested by some studies (NIH, NHLBI, 2007), measures to control dampness or fungal growth in the home seems logical and may be beneficial.

Outdoor Allergens

The strongest associations between mold-spore exposure and asthma have been with outdoor fungi, such as Alternaria, which is ubiquitous in the environment and is a natural part of fungal flora almost everywhere. Alternaria spores are airborne and found in the soil and water, as well as indoors and on objects. Alternaria species are capable of growing both indoors and out, on buccal mucosa, on eyelids, and within respiratory tracts. When inhaled they can produce toxic compounds that readily cause opportunistic infections in immunocompromised people such as AIDS clients. Inhalant allergen exposure to seasonal outdoor fungal spores has been implicated in fatal exacerbations of asthma.

Sensitization to outdoor pollens carries less risk for asthma, although exposure to grass and ragweed pollen has been associated with seasonal asthma exacerbation. Clients can reduce exposure during peak pollen season by staying indoors with windows closed in an air-conditioned environment, particularly during the midday and afternoon when pollen and some spore counts are highest. Conducting outdoor activities shortly after sunrise or in the evening hours will result in less exposure to pollen. These actions may not be realistic for some clients, especially children.

Food Allergens

Food allergens are not a common precipitant of asthma symptoms. Foods are an important cause of anaphylaxis in adults and children, but significant lower respiratory tract symptoms are uncommon even with positive double-blind food challenges (NIH, NHLBI, 2007). However, asthma is a risk factor for fatal anaphylactic reactions to food or immunotherapy.


In addition to questioning clients about exposure to common inhalants whose presence can be confirmed through allergen testing, the clinician must also consider the role of irritants such as tobacco smoke, air pollution, and indoor chemical pollution on the course of the disease.

Environmental Tobacco Smoke

Exposure to environmental tobacco smoke (ETS) is common in the United States. Environmental tobacco smoke is associated with increased respiratory symptoms, decreased lung function, and greater use of health services among those who have asthma in all age groups, although negative effects may vary by age (NIH, NHLBI, 2007). Exposure to maternal smoking has been shown to be a risk factor for the development of asthma in infancy and childhood. Effects of ETS on a child’s asthma are known to be more severe when the mother smokes than when others in the household smoke. Heavy smokers may be less aware than light smokers of the effects of ETS exposure on children (NIH, NHLBI, 2007).

The primary modes of exposure to ETS for adults who have asthma may be when they are at work or traveling. This becomes problematic because people are less likely to ask for personal consideration when they are in a group or an unfamiliar setting. If the smoker happens to be the asthma clients’ superior, the request is even more unlikely, leaving the asthma client with few alternatives besides increasing the use of SABA.

Environmental tobacco smoke exposure operates as a cofactor in wheezing and predisposes the client to other insults such as infections. Smoking outdoors to avoid exposing others may not adequately reduce exposure for children. Encourage parents of children who have asthma not to smoke. Be prepared to refer them to resources to help them stop smoking.

Be sensitive to the difficulty most people experience in attempting to rid themselves of this habit; many who are not currently experiencing any negative effects from smoking cite such factors as better weight control and decreased anxiety as reasons they continue to smoke, making it difficult to convince them of the benefits. As a routine part of asthma care, clients should be counseled concerning the negative effects of smoking and ETS and supported in their efforts to become tobacco free.

Increased Pollution Levels

Increased pollution levels—especially particulate matter ≤10 micrometers, which includes nitric oxide (NO2), ozone, and sulfur dioxide (SO2) among others—have been reported to precipitate symptoms of asthma, increase SABA use, and increase ED visits and hospitalizations for asthma. Exposure to pollutants may increase airway inflammation, predicting increased need for short-term relief medications. When practical, asthma clients should avoid outdoor exertion as well as exercise when air pollution levels are high; they need to follow medical recommendations for followup care if an exacerbation occurs when weather or pollution are likely contributors.

Indoor Pollution

Indoor pollution in the form of formaldehyde and volatile organic compounds (VOCs)—which can arise from sources such as new linoleum flooring, synthetic carpeting, particleboard, wall coverings, furniture, and recent painting—have been implicated as potential risk factors for the onset of asthma and wheezing. Clinicians should advise clients to be aware of the potential irritating effects of newly installed furnishings and finishes.

Paints and finishes, furnishings and floor covering advertised as VOC free are now readily available, but are significantly more expensive than standard products, making them inaccessible to middle- or low-income earners. For comparison, a one-gallon can of standard indoor wall paint averages about $12 less per gallon than VOC-free paint. Floor coverings and furnishings have an even greater differential; thus, “green” products are being marketed to those with higher levels of income. Clients should be advised that, where strong sensitivities exist, money spent on avoidance of VOCs is best spent in the bedroom, where the asthma client spends the most concentrated period of time.

Unvented gas stoves and appliances cause increased indoor levels of NO2. Use of gas stoves for cooking has been associated with increased respiratory symptoms, including wheezing in school children and increased prevalence of bronchial hyper-responsiveness in atopic adults. However, data from the National Health and Nutrition Examination Survey III (NHANES III) did not suggest any impact of gas-stove use on pulmonary function or respiratory symptoms in other adults who have asthma. This can probably be explained by the larger surface area of adult lungs compared to pediatric lungs.

Infants at high risk for asthma who were exposed to higher levels of NO2—but levels currently not considered harmful—had increased days of wheezing and shortness of breath (NIH, NHLBI, 2007). When un-flued gas heaters in schools were replaced, NO2 levels decreased by two-thirds, accompanied by significant reduction in both daytime and nighttime asthma symptoms (NIH, NHLBI, 2007). This has important implications when evaluating children who are spending most of their day in a new school or daycare setting who experience an otherwise unexplained increase in symptoms.

Exposure to gas heaters and appliances in infancy has been found to be a risk for wheezing, asthma, and bronchial hyper-responsiveness in school-aged children. They also promote conditions favorable to house dust mites, making the effects additive. Fumes from wood-burning appliances or fireplaces can exacerbate symptoms in persons who have asthma. Adults and children who depend on fires for their main heat source may have symptoms that are difficult to control, particularly if they live in a house that is relatively airtight, which prevents turnover of inside air. Sprays and strong odors, particularly perfumes, which have become ubiquitous in typical household and laundry cleaning products, can also irritate the lungs and precipitate asthma symptoms.

Occupational Exposures

Early recognition and control of exposures are particularly important in occupationally induced asthma. The longer an exposure occurs the less likely the worker is to be able to isolate and avoid an offending agent, and the more sensitized they are to the offending agent. Occupational asthma is suggested by a correlation between asthma symptoms and work, as well as with improvement when away from work for several days.

In particular, isocyanates are a volatile family of chemical agents used widely in the manufacture of common household items including foams, clothing with spandex fibers, shoes, carpet padding, insulation, mattresses, automobiles, car seats, and other products too numerous to name. In 1974 the Occupational Safety and Health Association (OSHA) began publishing safety standards for industrial workers—including those working in shipyards, construction, the auto industry and others—advising of risks from isocyanates with symptoms ranging from rashes to respiratory symptoms. Since then, more data has accumulated on these chemicals because their use continues to proliferate and they appear in more everyday products.

More information on this category of chemicals can be gained by going to the OSHA website and looking up isocyanates. General Industry Standards are recommended in publication number 29CFR1910, which summarizes workplace safety standards, including those involving management of highly hazardous chemicals.

The list of potential sources of exposure permeates our society, with the greatest burden being borne by those workers who are employed in manufacture and especially those in closed environments with poor ventilation. In addition to being able to provoke and exacerbate asthmatic symptoms, isocyanates are listed as potential human carcinogens. Twenty-five states, plus Puerto Rico and the Virgin Islands, have OSHA-approved state plans and have adopted their own standards and enforcement policies in an attempt to minimize exposure. However, of the twenty-five, the plans for Connecticut, Illinois, New Jersey, New York, and the Virgin Islands cover public-sector employment only.

Occupational exposure should be considered when the following are present.

Potential for workplace-related symptoms

  • Recognized sensitizers (eg, isocyanates, plant or animal products)
  • Irritants or physical stimuli (eg, cold/heat, dust, humidity)
  • Coworkers who have similar symptoms

Patterns of symptoms (in relation to work exposures)

  • Improvement occurs during vacations or days off (may take a week or more).
  • Symptoms may be immediate (<1 hour), delayed (most commonly, 2–8 hours after exposure), or nocturnal.
  • Initial symptoms may occur after high-level exposure (eg, a spill).

Many clients may fail to associate their symptoms with work, because symptoms often begin several hours after exposure. Recently, common jobs—such as domestic cleaner, laboratory technician, and house painter—have been associated with increased rates of asthma (NIH, NHLBI, 2007). Serial peak flow records at work and away from work can confirm the association between work and asthma. Workplace exposure to sensitizing chemicals, allergens, or dusts can induce asthma that persists after the exposures are terminated. This effect should be distinguished from allergen- or irritant-induced aggravation of pre-existing asthma.

Client confidentiality issues are particularly important in work-related asthma. Even general inquiries about the potential adverse health effects of work exposures may result in reprisals against the client. Clients who have asthma need to be informed of this possibility and be full partners in the decision to approach management regarding control of workplace exposures. If possible, they should be referred to specialists in workplace exposure to help protect them from reprisals or dismissal. In the current work climate, it is vital that asthmatic clients be fully informed of the potential for employer retaliation because job loss may trigger loss of health insurance.

If clients elect to pursue workplace exposure, their concerns are more likely to be taken seriously if they can provide objective findings that show symptoms being provoked consistently by conditions present in the workplace. Clients being evaluated for possible work-related exposure should be taught to do serial documentation for 2 to 3 weeks, including up to 2 weeks of work followed by 1 week away from work, and to:

  • Record when symptoms and exposures occur
  • Record when a SABA is used
  • Measure and record peak flow (or FEV1) every 2 hours while awake

Early recognition and control of factors such as inhalant allergens, irritants, and workplace exposure is critical in the overall management of asthma. The goal of medication management should always be directed at measures that minimize the complexity and intensity of medications, using the lowest doses necessary to maintain control of symptoms.

Managing risk factors is essential to stabilizing the disease and calls for a comprehensive history to discover any existing factors that make asthma more difficult to control and manage. Upon diagnosis, ask questions of the client (or caretaker) that reveal patterns of exposure in order to associate possible triggers with active symptoms. To start, determine the frequency and extent of the client’s exposure to allergens and irritants. Be sure to consider the possibility that exposures are taking place away from the client’s home.

Sample Questions for Identifying Factors That Can Exacerbate Asthma

These questions are provided as examples and have not been assessed for validity and reliability. Source: Adapted from NIH, NHLBI, 2007.

Inhalant allergens

  • Does the client have symptoms year round? (if yes, proceed with focused questions)
  • Does the client have pets? Are they kept indoors?
  • What types of pets?
  • Is there dampness or moisture in any room of the house?
  • Is there mold visible in any room in the house?
  • Has the client seen cockroaches or rodents in the house?
  • Are symptoms worse when carpets and upholstered surfaces are being vacuumed?
  • Is there a swamp cooler in the house?
  • Do the client’s symptoms worsen at certain times of the year? (if yes, determine when)
    • Early spring (trees)
    • Late spring (grasses)
    • Late summer and autumn (weeds)
    • Summer and autumn (Alternaria, Cladosporium, mites)
    • Cold months in temperate climate (animal dander)

Tobacco smoke

  • Does the client smoke?
  • Is the client exposed to secondhand smoke in the home, in a car, or at work, daycare, or school?

Indoor/outdoor pollutants and irritants

  • Is there a wood-burning stove or fireplace used in the home? Main source of heat?
  • Are there other unvented stoves or heaters in the home?
  • Is the client exposed to strong odors or fumes from scented products, cleaning agents, or sprays?
  • Have there been recent renovations or painting in the home?

Workplace exposures

  • Does the client cough or wheeze during the week but not on weekends or when away from work?
  • Do the client’s eyes or nasal passages become irritated soon after arrival at work?
  • Are there co-workers with similar symptoms?
  • What agents are known to be used in the workplace?

With this additional information in mind, let’s revisit our student Tom, who improved when he implemented measures to control his reflux. Another month has elapsed since he was seen and he has returned to the office for his routine scheduled appointment. He has been on his inhaled cortico­steroid for 6 weeks total and has taken no further oral prednisone. He does, however, find that on most days he needs to use his SABA in the evening after he has been home for several hours, and occasionally again in the morning. Tom is requesting a refill on his albuterol (SABA), which he has had for only 6 weeks.

Tom keeps his door closed during the day so the cat doesn’t sleep on his bed. When home, he leaves his door open so he can carry on conversations with his roommate. Tom’s room in the apartment is in the back and is actually a converted porch containing numerous houseplants, which are a hobby for Tom. Tom doesn’t smoke but his roommate does; however, Tom says the roommate only smokes outside. Tom’s bed is an aging foam futon placed on the floor, which he thinks is synthetic carpet over concrete. When asked about the possibility of cockroaches or rodents Tom is sheepish, shrugging his shoulders: “You know what it’s like when it’s just a couple of guys.” He is certain there are no mice or other rodents: “The cat takes care of that.”

This level of exposure to allergens and irritants is not unusual. Without obtaining this additional input, his clinician might simply keep increasing Tom’s medications when he needs education about the effect these exposures are having on his asthma. He has used an entire canister of albuterol in 6 weeks. Each canister typically has 200 actuations, or 100 doses if a dose is 2 puffs. The Rule of Two recommends two canisters a year as a standard to measure control. It is probable that Tom is using the SABA more frequently than he realizes, since he was not advised to keep a symptom diary and has no written Asthma Action Plan to help monitor his symptoms. Unless a comprehensive survey is included as part of his plan of care, it is likely that he will quickly move to a more complicated medication regimen with more potent drugs. (This may be necessary in any event, depending on his willingness and ability to make changes.)

At this point, it is critical to develop a cooperative healthcare partnership that has a strong component of education and emphasizes self-care principles, while negotiating agreements about the goals of treatment, specific medications, and the actions Tom will take to reach the agreed-upon goals.

Tom has persistent asthma. Although his initial response to medication appeared good, continued exposure to allergens and irritants is complicating management. He is at risk for further exacerbation and seems destined to have further deterioration if steps are not taken to improve control. He is open to allergy testing, agreeing that he has significant exposures. He is amenable to this approach because he likes the idea of being able to “see” the results.

Other Causal Factors

Other factors can cause asthma exacerbations in some individuals. These include the use of aspirin, NSAIDS, beta blockers, and sulfite-containing foods.

Aspirin and NSAIDS

Some client’s asthma symptoms are precipitated when they take aspirin or other nonsteroidal anti-inflammatory medications (NSAIDs). Clients who have sensitivity to aspirin often have cross sensitivity to NSAIDs, and vice versa. Up to 21% of adults and 5% of children may have this response and, when they do, the potential exists for a severe or fatal exacerbation.

Alternatives to aspirin that usually do not cause acute bronchoconstriction in aspirin-sensitive clients include acetaminophen or the cox-2 inhibitor celecoxib (Celebrex). However, care should be taken when making these recommendations because neither of these alternatives is risk-free. New guidelines for acetaminophen have emerged because the risk for liver failure is much greater than previously suspected. Moreover, even the generic form of celecoxib is relatively expensive and may not be covered by an insurance plan.

The prevalence of aspirin sensitivity increases with age and severity of disease, and aspirin may appear in products not specifically aimed at treating pain and fever. In cases where a co-morbid condition necessitates use of aspirin, desensitization treatment followed by daily aspirin therapy may be undertaken with the supervision of a specialist qualified to treat the condition and manage reactions that can include anaphylaxis.

Beta Blockers

Beta Blockers are in a class of drugs often used to treat hypertension and other cardiac conditions. They are also used occasionally for the off-label management of mood disorders, migraine syndrome, and other chronic conditions that do not respond to conventional therapies. As a group, beta blockers are further classified as either cardiac-selective or noncardiac-selective. Some asthma clients who have milder forms of the disease may be able to tolerate some of the cardiac-selective forms. This therapy should only be undertaken as a last resort, and careful supervision must continue for the duration of therapy. Some ophthalmologic drops containing beta blockers are used to treat glaucoma; these should be avoided in asthma clients sensitive to beta blockers.


In clients with severe persistent asthma, sulfite-containing foods have caused severe asthma exacerbations. Sulfites can be found in processed and preserved foods such as potato products, shrimp, dried fruits, beer and wine, among others. Clients should be educated to read labels for sulfite and avoid those products.

Though food allergies are known to have serious and potentially fatal outcomes in a sensitized individual, there is no immunotherapy that has been successful in treating these potential triggers. Education to identify and avoid these agents is the only treatment known to prevent a potential IgE-mediated response to food allergy. Clients are still encouraged to eat a varied and well-balanced diet containing fruit, vegetables, and whole grains, while excluding foods that increase symptom severity.

Now that the roles of triggers and abatement measures are more fully understood, let us go back to the case of Tom, who has returned to his primary care provider’s office after seeing an allergist, who confirmed that Tom has severe sensitivity to cat dander and moderate sensitivity to mold and house dust mites. He does not appear to be sensitive to cockroach droppings. With this information we can make recommendations to Tom that will help him gain control of his asthma.

Test Your Knowledge

Recommendations that Tom be tested for specific allergens are based on:

  1. Client report of symptoms.
  2. A history positive for triggers.
  3. Client-requested testing.
  4. A history positive for exposure to allergens and symptoms.

Tom asks you which of his triggers can be confirmed through testing. You reply:

  1. Irritants such as smoke and inhalants, including dander, mites, and mold.
  2. All inhalants, including isocyanates.
  3. Inhalants such as dander, mites, and mold.
  4. Inhalants such as dander, mites, and mold and irritants such as sulfite.

When counseling Tom regarding his allergen exposure, you inform him:

  1. He must immediately move to housing with no cats or his condition will deteriorate.
  2. If removing the cat is objectionable, he must take steps to minimize cat dander exposure including keeping the cat out of his room, keeping his door closed, and keeping the cat off upholstered surfaces in the house.
  3. If removing the cat is objectionable, a HEPA filter placed in Tom’s room will remove dander from the immediate environment, which should help manage exposure
  4. No measures are necessary because there is no positive correlation at this time between allergen exposure and symptom exacerbation.

Tom is agreeable to making changes to reduce his exposure to cat dander and asks if there are more things he can change that might be helpful. You advise him that the next priority area would be:

  1. Ensuring that all food is contained and garbage placed in sealed containers.
  2. Removing the carpet in his bedroom because it is placed over concrete.
  3. Washing his bedding regularly to eliminate mites.
  4. Encasing his mattress and pillow in allergen covers and washing his bedding weekly in hot water over 130°F.

Tom is considering immunotherapy to help manage his response to cat dander and wants to know your thoughts, so you:

  1. Recommend immunotherapy highly because it will cure his cat allergy forever.
  2. Discourage immunotherapy because the serum available against cat dander is not very effective.
  3. Discourage immunotherapy knowing that his continued exposure to cat dander will make the therapy ineffective.
  4. Recommend immunotherapy with the provision that he commit to a course of treatment that will take 3 to 5 years to complete before response can be completely determined.

Answers: D,C,B,D,D


Immunotherapy is usually reserved for patients whose symptoms occur all year or during a major portion of the year and in whom controlling symptoms with pharmacologic management is difficult because the medication is ineffective, multiple medications are required, or the patient is not accepting the use of medication.

Controlled studies of immunotherapy, usually conducted with single allergens, have demonstrated reduction in asthma symptoms caused by exposure to grass, cat, house dust mites, ragweed, Cladosporium, and Alternaria. A meta-analysis of seventy-five randomized, placebo-controlled studies has confirmed the effectiveness of immunotherapy in asthma, with a significant reduction in asthma symptoms and medication and with improvement in bronchial hyperreactivity (NIH, NHLBI, 2007). This meta-analysis included 36 trials for allergy to house dust mites, 20 for pollen allergy, and 10 for animal dander.

In the United States, standardized extracts are available for house dust mites, grasses, short ragweed, and cat, and there are non-standardized extracts of other pollens and for dog that appear to have similar potency. Available extracts for cockroach and mold, on the other hand, vary widely as to allergen content and allergenic potency, and their effectiveness in specific immunotherapy has not been demonstrated (NIH, NHLBI, 2007).

Few studies have been reported on multiple allergen mixes that are commonly used in clinical practice. One, which included high doses of all allergens to which the children were sensitive, demonstrated reduction in asthma symptoms compared to lower doses of the same allergens or placebo. Another study, in which the children were given optimal medical therapy and in which the only perennial allergen administered was house dust mite, demonstrated no improvement in asthma symptoms between active and placebo therapy (NIH, NHLBI, 2007).

The course of allergen immunotherapy is typically of 3 to 5 years’ duration. Severe and sometimes fatal reactions to immunotherapy, especially severe bronchoconstriction, are more frequent among patients who have asthma, particularly those who have poorly controlled asthma, compared with those who have allergic rhinitis. If use of allergen immunotherapy is elected, it should be administered only in a physician’s office, where facilities and trained personnel are available to treat any life-threatening reaction that can, but rarely does, occur. For this reason, enthusiasm for the use of immunotherapy in asthma differs considerably among experts (NIH, NHLBI, 2007).

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