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The Importance of Environmental Assessment and Avoidance in the Management of Patients with Allergic Rhinitis and Asthma
By Jonathan A. Bernstein, M.D.
Associate Professor of Medicine
University of Cincinnati College of Medicine
I. Introduction:
Approximately 56 million individuals or 20% of the United States population suffer from allergic rhinitis and 5% suffer from asthma.1 Recent epidemiology studies indicate that the prevalence of allergic rhinitis and asthma is increasing throughout the world including the United States. 2 It is widely believed that a major contributing factor to the rising prevalence of these disorders is poor indoor air quality. This hypothesis is supported by studies that have compared the prevalence of atopy and asthma among rural and urban populations. It was observed that atopy and asthma were more prevalent among rural inhabitants who moved to urban dwellings. 3 These striking differences point to the importance of domestic exposures in causing a greater predilection for atopy and asthma among urban dwellers.
Allergic rhinitis is the most prevalent chronic illness diagnosed in children below the age of 18 and the fifth most common chronic illness diagnosed overall. Patients with allergic rhinitis are at increased risk for developing asthma. 4 It is not surprising that the annual cost to treat allergic rhinitis in the United States exceeds three billion dollars. Recent economic predictions for the treatment of asthma the United States approach 13 billion dollars. 5 This economic burden is even more substantial if one factors in costs of treating sinusitis and otitis media, which are common complications of allergic rhinitis and asthma. 4 The significant morbidity and rising health care costs associated with allergic rhinitis and asthma necessitate that physicians become more proficient in the evaluation and treatment of these conditions.
Seasonal allergic rhinitis refers to patients with allergy symptoms triggered by pollen or mold spore allergens during either the spring, summer or fall. These seasons vary geographically throughout the United States.Symptoms may include sneezing fits (ie. 5-10 sneezes in succession), itching of the eyes, ears, nose, throat and palate, runny nose, watery/puffy eyes, nasal stuffiness, post-nasal drip, sinus pressure and fatigue. Triggers include being outdoors during the spring, summer and fall pollen seasons. Symptoms are typically worse when patients are outdoors and improve when they are indoors in an air-conditioned climate. 6 The patient will usually be able to distinguish whether symptoms occur seasonally, perennially or both. Perennial allergic rhinitis refers to year round hayfever symptoms that are triggered by indoor allergens such dust mites, cockroaches, mold spores, feathers and animal allergens. Symptoms include nasal congestion, postnasal drip, sinus pressure/headaches, ear plugging/ popping and may include any or all of the above seasonal allergy symptoms. Patients with both perennial symptoms and seasonal exacerbations are referred to as having perennial allergic rhinitis with a seasonal component. 6 Triggers may include dust, moldy environments, freshly cut grass, raking leaves, cats, dogs, birds and cockroach exposure. Perennial allergens such as dust mites, molds, animal allergens and cockroaches may be difficult to identify by history alone. Skin testing is necessary to confirm sensitization to these allergens but does not indicate that the individual is currently being exposed. 6
Conditions such as non-allergic rhinitis [vasomotor rhinitis (VMR) or non-allergic rhinitis with eosinophil syndrome (NARES)] can mimic allergic rhinitis. Patients with non-allergic rhinitis experience nasal congestion, postnasal drip, headaches/sinus pressure and ear plugging. Skin testing to seasonal and perennial allergens is negative. Triggers for non-allergic rhinitis include weather changes (temperature or barometric pressure changes), postural changes, irritants such as smoke, perfumes, potpourris, solvents, cleaning agents, incense and soaps/detergents to name a few. 6 Patients with allergic and non-allergic rhinitis components are said to have mixed rhinitis.
Asthma is a chronic obstructive inflammatory lung disease characterized by: 1) airway inflammation; 2) bronchial hyperresponsiveness and; 3) at least partial improvement of lung function after treatment with bronchodilator medication. 7 Untreated asthma can lead to airway remodeling or scarring of the airways that results in permanent loss of lung function. Typical asthma symptoms include wheezing, coughing, chest tightness and shortness of breath. However, many other conditions can present with symptoms that mimic asthma such as gastroesophageal reflux disease, post-nasal drainage from chronic sinusitis, congestive heart failure or pulmonary emboli to name a few. It is always important to remember that all that wheezes may not be asthma and all that is asthma may not wheeze. Common triggers for patients with allergic asthma include animals, dust mites, cockroaches, mold spores and pollen. Non-allergic triggers include viral upper respiratory infections, exercise, extreme temperature conditions such as cold or hot weather and a spectrum of irritants. 7
II. Environmental Determinants And Asthma:
Asthma is a very complex disease that is influenced by multiple genetic and environmental determinants. Debate is ongoing as to whether genetic or environmental factors are dominant in the overall development of asthma. However most studies now indicate that environmental exposures are very important in causing and aggravating asthma. This is exemplified best in monozygotic twin asthma studies, which have identified as high as 50% discordance for asthma among genetically identical probands. 8 This suggests that differences in environmental exposures may be important in the ultimate phenotypic expression of asthma. Recent scientific evidence also indicates that asthma is primarily an allergic mediated disease. Burrows et.al. reported in 1989 a strong correlation between total IgE levels, positive allergen skin test responses and asthma findings which have subsequently been confirmed by other investigators. 9 It is now also well established that patients with extrinsic (allergic) and intrinsic (non-allergic) asthma both express Th2 cytokines that are important for the development of asthma and other allergic diseases.
"Atopy", defined as the "genetic predisposition to develop allergic (IgE) antibodies in response to specific allergens", is now considered a risk factor for the development of asthma. The critical period for allergen sensitization appears to be during the first two to three years of life. 10 However, events may begin even earlier as researchers have shown that the developing fetus is capable of eliciting IgE-mediated responses to relevant allergenic stimuli as early as 22 weeks gestation. 11 In fact, current studies are now investigating whether environmental interventions initiated during the third trimester of pregnant women with a personal or family history of allergies and/or asthma would prevent or delay allergen sensitization and asthma in their babies. Preliminary data indicates that interventions have been successful at reducing allergen exposures and that there is a reduction in allergen sensitization and asthma in the group of children where such interventions were implemented. 12
A number of studies have been conducted to determine the relationship of allergenic stimuli in causing asthma and allergic rhinitis. To date, the dust mite has been the most extensively studied allergen. Dust mites are microscopic "spider like" creatures that have been demonstrated to be powerful allergens. The major allergens of dust mites come from their fecal waste particles and glandular secretions. 13 Dust mite allergens are primarily enzyme proteins, which may explain why they are very sensitizing. It is estimated that about 90% of people with allergies are sensitized to dust mites and over 70% of asthma patients are sensitized to dust mites. Dust mites thrive in humid environments and feed off human skin scales. They are most commonly found in bedding (pillows, mattresses, boxsprings, comforters), carpets and upholstered furniture. 13
Many studies have confirmed the relationship between dust mites and the development of asthma.
Sporik et. al. reported that exposure to house-dust mite in early childhood is an important determining factor for the later development of asthma. 14 Peat et. al. found that house dust mites are an important cause of childhood asthma and that reducing exposure to house dust mites at an early age could have a large public health benefit in terms of asthma prevention. 15 Subsequent studies have shown that when levels of dust mite allergen are reduced to very low levels (<2: g/gram of dust), dust mite sensitization and asthma can actually be prevented. 16
Animal allergens have also been confirmed to be important in causing and aggravating asthma and allergic rhinitis. It is estimated that over a third of the population has at least one or more cats in their home. This domestic pet has overtaken the dog in popularity probably because it requires low maintenance. Cat allergen is a very light allergen (3 microns in size) that is primarily released from the sebaceous (sweat) glands in the skin. Cat allergen can stay suspended in the air for five to six hours at a time and becomes airborne with minimal disturbance in the room.17 It sticks to walls, clothing, shoes, carpets, bedding and furniture and it is difficult to get rid of completely. Even after removing the cat from the home, residual cat allergen can be measured several months later.Lindfors et.al. found a strong relationship between cat exposure and sensitization. 18 In their study, they found a combination of dampness, passive smoke exposure and cat exposure with cat sensitization was strongly associated with subsequent development of asthma. Interestingly, recent studies have reported significant levels of cat allergen in homes where there are no cats indicating that cat allergen can be brought in from outside sources on shoes and clothing. 19 Siebers et.al. measured cat and dust mite allergen levels in the Antarctic where there are no cats and the relative humidity seldom rises above 20%. Surprisingly, they found dust mite allergen and even greater levels of cat allergen levels in the living environments sampled. This study confirmed that allergens can be passively transferred to local environments that would be unlikely to support their accumulation. 20 Ingram et. al. found high levels of cat and dog allergens in homes with cats and/or dogs. They found that cat and dog allergen sensitization was strongly associated with the development of asthma. 21 Sarpong et.al. found that children with combined sensitivity to cat, dog, dust mite and cockroach allergens were at increased risk of having a more severe form of asthma. 22 In addition, sensitization to cat allergen alone constituted a risk for more severe asthma in children. 22
Cockroaches are present in most homes even though they usually cannot be readily identified. In fact, if you see a cockroach during the daytime, this usually means there is major overcrowding of cockroach populations and significant infestation in the home. The two major species of cockroaches in the United States are German and American. 23 There is now a significant amount of evidence supporting a relationship between cockroach sensitization and asthma. Rosenstreich et. al. found that inner-city children with asthma are allergic to dust mites, cockroaches and cats. However, they found that cockroach allergen levels in the bedroom were approximately five times higher than dust mite and cat allergen levels. Children with cockroach allergy and high cockroach bedroom exposure levels were at a much greater risk for hospitalization and unscheduled medical visits for their asthma and had more asthma symptoms overall compared to other children with asthma not sensitized to cockroach. 24 The combination of cockroach sensitization and high levels of cockroach exposure may explain the increased frequency of asthma reported among inner-city children. Sarpong SB et. al. reported that being African-American and having a low socioeconomic status were significant independent risk factors for cockroach allergen sensitization in children with atopic asthma. 25
Many other factors have been found to be potentially important for the later development of asthma and allergies. Maternal history of asthma, maternal smoking during pregnancy, low birth weight, lack of prenatal care, passive smoke exposure, duration of breast feeding after birth, birth order, moldy/humid living environments and recurrent viral infections or bronchiolitis in the first few years of life have all been reported to increase the risk for the development of asthma. 26
III. Effectiveness of Environmental Interventions in the Treatment of Asthma:
Many studies have been conducted to investigate the effects of environmental interventions on reducing allergen levels and improving asthma and allergy symptoms. These studies are very labor intensive and require continual assessment for at least six months to a year before changes in clinical outcomes can be identified. The sentinal study, which demonstrated the effectiveness of allergen intervention in improving asthma was conducted in Davos, Switzerland. 27 Children from an urban environment with asthma and dust mite sensitization were sent to a sanitarium located on a mountain in Davos where dust mite allergen levels are very low. After one year, the degree of bronchial hyperresponsiveness measured in these children at baseline either significantly decreased or completely disappeared. Many children were able to decrease or discontinue medications. Follow-up of these children after returning to their homes in the city revealed that their asthma symptoms and bronchial hyperresponsiveness had returned. 27
Subsequent studies have looked at more practical environmental control interventions. Bedding encasements have been conclusively demonstrated to reduce dust mite exposure and prevent asthma symptoms. Ehnert B et. al. found that bedding encasements were successful in reducing dust mite allergen levels by 98% and in reducing bronchial hyperresponsiveness in dust mite sensitized children with asthma. 28 Maintaining dust mite levels between 2µg to 10µg/gm of dust, levels that have been relatively innocuous for dust mite sensitization and asthma, was possible to accomplish with encasements alone in this study. 28
Murray et.al. randomized dust mite sensitized children with asthma between two groups. One group received dust mite protective bedding and aggressive house cleaning whereas the other group received no intervention. After one month, the asthmatic children receiving dust mite avoidance measures demonstrated significant improvement in asthma measured by reduction in symptoms and medication requirements. They also experienced improvement in peak flow measurements and histamine-induced bronchial hyperresponsiveness. 29
Dehumidification has also been studied as an important intervention for dust mite control. Arlian et.al. found that maintaining daily indoor relative humidity below 50%, even when the relative humidity is above 50% for two to eight hours a day, effectively reduces dust mite growth and production of allergen. 30 They concluded that maintaining the relative humidity below 35% for at least 22 hours a day is necessary to completely eliminate dust mites. 30 Cabrera et. al. also reported that dust mite allergen levels were significantly reduced by more than 50% after the use of a dehumidifier in the living environment. The authors concluded that dehumidification was a simple and effective way to control dust mites, especially in humid climates. 31
Removing carpets and replacing them with tile, linoleum or hardwood flooring has been found to reduce the amount of indoor dust mite allergen. However, this recommendation is not always affordable or practical. Using special HEPA (high efficiency particulate air) vacuum cleaners and to a lesser extent standard vacuums with double layered bags, has been demonstrated to pick up dust from carpets more efficiently and reduce airborne dust while vacuuming. Vaughan and coworkers recently reported that vacuum cleaners designed with HEPA filters and microfiltration bags leaked significantly lower amounts of allergens than standard vacuums and vacuum bags.32 Hegarty et. al. compared four microfiltration vacuum cleaners to a conventional upright vacuum cleaner using standard bags or special bags with 0.1µm pore size. They found that the microfiltration vacuum cleaners produced lower levels of airborne dust mite allergens compared to the conventional vacuum cleaner with or without the special bags. There was variability between the microfiltration vacuums in how much dust was actually retrieved. This study indicated that vacuums with special filter systems were more effective in collecting more dust and preventing airborne dust mite allergen levels during vacuuming.33 Frequent vacuuming with a HEPA vacuum or standard vacuum with double layered bags has also been demonstrated to help reduce cat allergen in carpets. Woodfolk et. al. studied the effectiveness of four groups of vacuum cleaners in controlling airborne cat allergen during vacuuming. Vacuum cleaners with double-thickness vacuum bags and HEPA filtration were effective in retaining cat allergen in contrast to the other models studied where allergen was noted to leak. Some models if modified with an electrostatic filter also had improvement in the ability to capture and retain allergen. 34
Many studies have been conducted to investigate the effectiveness of carpet treatments which either kill dust mites or denature dust mite allergens. Woodfolk et.al. found that benzyl benzoate and tannic acid reduced airborne dust mite allergens by more than 64%.35 The percent change in dust mite levels after treatment was significantly greater than for untreated carpets. However, the same reductions were not found for cat allergen. Repeated applications with tannic acid were necessary to maintain reduced allergen concentrations. 35 Chang et.al found that the addition of benzyl benzoate to conventional house dust mite avoidance measures resulted in a significant reduction in floor carpet dust mite levels that persisted up to three months.36
Recent studies support the need to use multiple interventions in the home to effectively reduce dust mite allergen levels. van der Heide et.al. compared the effect of mattress encasings, with or without application of benzyl benzoate, on the mattress, bedroom and living room carpets on improving lung function and airway hyperresponsiveness in dust-mite sensitized asthmatics.37 Airway hyperresponsiveness significantly improved in those groups that received mattress encasements. A small, but statistically significant, change in airway hyperresponsiveness was detected in the group that also received benzyl benzoate.37
Finally, a recent study reported that HEPA free standing filters can reduce airborne cat allergen levels in the bedroom and living room. The reduced levels of cat allergen resulted in improved lung function and reduced asthma symptoms in patients with cat-induced asthma symptoms.38 Studies have shown a similar effect in reducing airborne dog allergen levels and improving clinical outcomes.39
Cockroach management and control is possible but requires persistence. Cockroach allergen levels can persist for several months after extermination. Furthermore, there are no effective methods that can kill cockroach eggs. To effectively control cockroach populations and allergen levels, interventions must be conducted on a regular basis every one to two months. Sarpong et.al. investigated the effects of extermination every 6 months in an urban dormitory infested with cockroaches.40 Rooms were vacuumed once a week and carpets were shampooed once a year. Dust sampling for cockroach allergen revealed that extermination was effective at significantly reducing cockroach allergen levels.40 Eggleston et.al. intervened in 13 inner-city homes infested with cockroaches. Each home was professionally cleaned by vacuuming and thorough cleaning of the kitchen.41 Pesticides were placed in the kitchen and other parts of the home every month up to eight months at which time dust samples were also collected. The results of this study revealed that extermination was effective in killing cockroaches but standard housecleaning procedures were only partially effective in removing the residual cockroach allergen during this study period.41 Williams et.al. found that the number of living cockroaches is greatly reduced by extermination procedures. However the amount of cockroach allergen decline does not appreciably occur over a period of six months. The authors speculated that longer time periods are required to reduce cockroach allergen levels.42 Additional studies are required to determine the most effective and safest strategies for reducing cockroach allergen levels.
IV. National Heart Blood Lung Institute Guidelines For Asthma: Rationale For Implementation Of Environmental Control Measures:
The aforementioned studies strongly support the relationship between allergen exposure, sensitization and the development of allergic rhinitis and/or asthma. Furthermore, many studies have demonstrated that appropriate interventions can reduce indoor allergen exposure and improve clinical outcomes. There is now a consensus opinion that avoidance of allergens and/or irritants known to cause or aggravate allergic rhinitis and/or asthma should be a central component in the management of patients with these disorders. The National Heart Lung Blood Institute has released revised guidelines for the management and treatment of asthma in 1997. These guidelines are divided into four categories: 1) Assessment and Monitoring; 2) Avoidance of triggers known to cause asthma; 3) Pharmacologic therapy and; 4) Education.43 However, in spite of the wide dissemination of these guidelines, the prevalence, morbidity and mortality of asthma continue to rise in the United States. This has resulted in a staggering rise in health care costs associated with the management of this disease. It is essential that physicians critically address each of these components while managing their patients with asthma. It is important to emphasize that history alone is not sensitive or specific enough to making a definitive diagnosis of asthma. Therefore, diagnosis of asthma should be made using objective as well as subjective criteria. Asthma, like hypertension and diabetes mellitus, is a chronic illness. Physicians would not start a patient with high blood pressure on anti-hypertensive medications or a patient with diabetes mellitus on insulin without first confirming the diagnosis using a blood pressure cuff or blood sugar measurements, respectively. The same analogy should be applied to asthma. If asthma is diagnosed, most patients will require controller medications to prevent smooth muscle dysfunction and airway inflammation, the two cardinal pathogenic features of this chronic inflammatory lung disorder. Therefore, pulmonary function testing should be performed before and after bronchodilator medications to determine if there is at least a 12% improvement in FEV1. If spirometry is normal but the history is suggestive of asthma, peak flow monitoring over two to three weeks to assess for diurnal variability greater than 20% may be helpful for establishing a diagnosis. Finally, either a definitive diagnosis or exclusion of asthma can be made with a methacholine challenge test. The effort and costs to confirm a definitive diagnosis of asthma is miniscule compared to the erroneous treatment costs of this chronic disease that could occur. Continuous monitoring using a peak flow meter or newer computerized flow meters is useful for both the physician and patient in assessing response to treatment and early deterioration of lung function, which may be preludes to an asthma exacerbation.
The second component of the NHLBI guidelines recommends avoidance of triggers that cause asthma.43 This necessitates a very thorough environmental history at home and work. Unfortunately, history alone has not been shown to be a sensitive method for identifying environmental exposures. 44 Preferably, a walk through the home or workplace is recommended for identifying the sources and magnitude of allergen and/or irritant exposures. Unfortunately, this can prove costly and very time consuming for the physician, patient and/or employer. Currently, recommendations for avoidance measures are based on history and allergy skin testing, the preferred method for identifying whether a patient is sensitized to one or more allergens. However, skin sensitization alone does not indicate that the patient has clinical allergies or that they are currently exposed to the offending allergen. The physician must correlate skin test results to the patient’s history and environmental exposure to confirm allergies. To further complicate matters, patient compliance with avoidance measures is generally poor. Studies indicate that only 10-30% of allergic patients implement environmental interventions.45 Given the importance of reducing exposure to asthma triggers, a greater effort by physicians and allied health personnel is necessary to improve patient compliance with avoidance measures.
Educating patients about the relationship between allergens and asthma is the first step for improving compliance.43 To accomplish this formidable task, it is necessary to increase the awareness of patients, employers and physicians about indoor air quality and allergen exposure. One approach to increased awareness about environmental allergen exposure(s) would be to collect dust and/or air samples that could be quantitatively analyzed for perennial allergens. The traditional approach for assessing indoor air quality requires services of a professional experienced in dust and air sampling methods. These analyses can be costly and may not always be warranted. A more practical approach would enable the patient to collect dust samples from different rooms in the home or workplace and send these to a central laboratory for analysis at an affordable price. This information would enhance the physician’s management of asthma and allergies by allowing more precise tailoring of individual recommendations for environmental control. Dust sampling would also allow the patient to monitor the effectiveness of environmental control measures in reducing indoor allergen levels. Therefore, an affordable and reliable indoor allergen detection method that identifies allergen exposure is the missing piece of the puzzle that connects allergen sensitization to clinical symptomatology. Allergen detection should increase compliance with environmental control measures just as peak flow meters and spirometry are intended to improve diagnosis of asthma and compliance with controller medications. Figure 1 is a proposed algorithmic approach for incorporating environmental assessment into the sequential evaluation of patients with allergies and asthma.
V. Conclusions:
In summary, comprehensive management of patients with allergic rhinitis and/or asthma requires an integrative approach. Evaluation should incorporate allergen testing to identify causes and/or triggers and indoor allergen detection for correlation of allergen sensitization with environmental exposure. In this manner, the physician can make more specific and efficient recommendations regarding environmental control measures. As in the treatment of any chronic illness, repetitive education and behavioral modification are essential for convincing the patient about the importance of this integrative approach in the management of his/her chronic disease.46
VI. References:
Lancet 1999;353:1942.
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