Approximately 56 million Americans (20% of the population) suffer from allergic rhinitis, and about 5% have asthma.1 Recent epidemiologic studies indicate that the prevalence of allergic rhinitis and asthma is increasing in the United States and throughout the world.1,2
Indoor environmental allergen exposure is widely believed to be a major contributing factor to the rising prevalence of these disorders. This hypothesis is supported by studies that have compared the prevalence of atopy and asthma among rural and urban populations and found that these conditions were more prevalent among rural inhabitants who moved to urban dwellings.1,3 This striking finding highlights the importance of domestic exposures in creating susceptibility to atopy and asthma among urban dwellers.
In this article, I review the environmental determinants of allergic rhinitis and asthma. In a second article I address the importance of allergen avoidance measures in patients with these conditions and review interventions directed at reducing exposure to dust mite, pet, and cockroach allergens.
The annual cost of treating allergic rhinitis in the United States exceeds $3 billion. The annual cost of asthma treatment is estimated at nearly $13 billion per year.1,4 This economic burden is even more substantial if one factors in the costs of treating sinusitis and otitis media, which are common complications of inadequately treated allergic rhinitis.1,5 The significant morbidity and rising health care costs associated with allergic rhinitis and asthma mandate that physicians become more proficient in the evaluation and treatment of these conditions. The triggers and symptoms of rhinitis and asthma are reviewed in the Table.
Allergic rhinitis. This is the most prevalent chronic illness diagnosed in children younger than 18 years and the fifth most common chronic illness diagnosed overall. Persons with allergic rhinitis are at increased risk for asthma.1,5 Seasonal allergic rhinitis refers to the presence of allergy symptoms triggered by pollen or mold spore allergens during the spring, summer, or fall. These pollen and mold spore seasons vary geographically throughout the United States.
Symptoms may include sneezing fits (5 to 10 sneezes in succession); itchiness of the eyes, ears, nose, throat, and palate; runny nose; watery/puffy eyes; nasal congestion; postnasal drip; sinus pressure; and fatigue. Symptoms are typically worse when patients are outdoors during pollen seasons and improve when they are indoors in an air-conditioned environment.1,6 Patients usually can distinguish whether symptoms occur seasonally, perennially, or both.
Perennial allergic rhinitis refers to year-round symptoms that are triggered by indoor allergens, such as those from dust mites, cockroaches, mold spores, feathers, and animals. Symptoms include nasal congestion, postnasal drip, sinus pressure/headaches, and ear plugging/popping and may include any or all of the above seasonal allergy symptoms.
Patients with both perennial symptoms and seasonal exacerbations are considered to have perennial allergic rhinitis with a seasonal component.1,6 Triggers may include outdoor pollens and indoor allergens such as dust mites; mold spores; and exposures to cats, dogs, birds, and cockroaches. Perennial allergens, such as those from dust mites, molds, animals, and cockroaches, may be difficult to identify by the history alone. Skin testing is necessary to confirm sensitization to these allergens but does not indicate that the person is currently being exposed.1,6
Conditions such as nonallergic rhinitis (vasomotor rhinitis or nonallergic rhinitis with eosinophil syndrome) can mimic allergic rhinitis. Patients with nonallergic rhinitis experience nasal congestion, postnasal drip, sinus pressure/headaches, and ear plugging. Results of skin testing for seasonal and perennial allergens are negative.
The triggers for nonallergic rhinitis include weather changes (both temperature and barometric pressure changes); postural changes; and irritants, such as smoke, potpourri, perfumes, cleaning agents, solvents, incense, and soaps or detergents.1,6 Patients who have allergic and nonal- lergic rhinitis components are said to have mixed rhinitis, which may occur in up to 50% of patients presenting with rhinitis symptoms.
Asthma. This chronic obstructive inflammatory lung disease is characterized by airway inflammation, bronchial hyperresponsiveness, and at least partial improvement of lung function after treatment with bronchodilator medication.1,7 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, such as gastroesophageal reflux disease, postnasal drainage from chronic sinusitis, vocal cord dysfunction, congestive heart failure, and pulmonary emboli, can present with symptoms that mimic asthma. 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. Nonallergic triggers include viral upper respiratory tract infections, exercise, extreme temperatures, and a wide spectrum of irritants.1,7
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