Allergic Rhinitis: Update on Diagnosis
Allergic Rhinitis: Update on Diagnosis
Key words: allergic rhinitis, nonallergic rhinitis, primary care
Allergic rhinitis is highly prevalent; about 20% of adults in the United States1 and 25% of children worldwide2 are affected. It is a major societal expense, with direct costs, attributable to physician visits and medications, of up to $5 billion per year, and indirect costs, mainly stemming from lost productivity, of up to $9.7 billion per year.3 In the United States, allergic rhinitis results in 3.5 million lost workdays and 2 million lost schooldays each year.4
In addition to the nasal and ocular symptoms of the disease, allergic rhinitis is associated with a higher burden of asthma and sinusitis.5 It also affects multiple areas related to quality of life, including quality of sleep,6,7 mood and energy level,4 work effectiveness,8 and even sexual function.9
Because nearly all patients with allergic rhinitis who seek medical attention present first to their primary care physician,1 this 2-part series will focus on the diagnosis and management of allergic rhinitis in the primary care setting. Here we discuss issues related to diagnosis, including the various types of rhinitis, complicating factors, common physical findings, and allergy` testing. In a coming issue, we will detail the treatment options.
ALLERGIC VERSUS NONALLERGIC RHINITIS
While the term “rhinitis” suggests that inflammation of the upper airway would be a cardinal feature, some forms of rhinitis do not involve inflammation. Rather, the term refers to the presence of one or more of the following10:
• Nasal congestion.
• Anterior or posterior rhinorrhea.
Causes of rhinitis are divided most broadly into allergic and nonallergic (Table).1,10,11
Allergic rhinitis. The usual onset is before age 20. Allergic rhinitis is caused by an IgE-mediated reaction to specific seasonal or perennial aeroallergens.11 Since the indoor environment is relatively invariant, associated allergens (most commonly dust mite, mold, pet dander, and cockroach) cause perennial symptoms. Outdoor allergens, including pollens, mold, and bioaerosols such as those from grass cutting (which can also function as nonallergic irritants), tend to cause seasonal symptoms, although there is regional variability because certain pollens have a seasonal presence in some areas but are present year-round in other areas.10
In allergic rhinitis, specific IgE antibodies to allergens develop and are displayed on the surface of mast cells. When allergen binds the mast cell–bound antibody, the mast cells release cytokines, leading within minutes to an early response that consists of sneezing, itchiness, congestion, rhinorrhea, and even constitutional symptoms (hence the term “hay fever”). These cytokines also attract other inflammatory cells to the nasal mucosa, in what is referred to as the second, or late-phase, allergic rhinitis response, which prominently features nasal congestion.12
Nonallergic rhinitis. This type of rhinitis does not involve IgE. Pure allergic rhinitis is thought to be about 3 times more prevalent than pure nonallergic rhinitis; however, a mixed picture of the two is quite common: it is estimated that 44% to 87% of patients with rhinitis have some component of mixed rhinitis.10 Nonallergic rhinitis has a slight female predominance and has a later age of onset, generally in adulthood, than allergic rhinitis.13
There are several subtypes of nonallergic rhinitis. Vasomotor rhinitis is an incompletely understood entity thought to involve neurally mediated hypersecretion and hyperemia in the nasal mucosa; it is ultimately a diagnosis of exclusion in patients whose allergy test results are negative.10,13,14 Triggers for this subtype include exercise, changes in temperature or humidity, alcohol ingestion, and inhaled irritants, such as tobacco smoke, perfume, and chlorine gas.13
Gustatory rhinitis refers to rhinorrhea induced by eating; it is thought to be vagally mediated and not allergic. Although allergic reactions to food can induce rhinitis, such reactions are almost always seen in concert with an urticarial rash, respiratory symptoms, and/or GI symptoms.15 Gustatory rhinitis generally occurs in older patients, most commonly in reaction to spicy foods, but some patients have rhinorrhea in response to a wide range of foods.16
Drug-induced rhinitis can occur with the use of a number of medications, including angiotensin-converting enzyme (ACE) inhibitors, hydrochlorothiazide,β-blockers, α1-blockers, central α2-agonists, and phosphodiesterase-5 inhibitors.13 When related to rebound congestion from overuse of nasal α-adrenergic agonists such as oxymetazoline, the syndrome is referred to as rhinitis medicamentosa.