KEY POINTS FOR CLINICIANS
- Physical clues to allergic rhinitis include boggy, pale, or “bluish” nasal turbinates, with watery discharge on nasal speculum exam. Patients may also have a nasal crease on the external nose caused by repeated rubbing or itching (the so-called “allergic salute”).
- Skin prick testing can detect IgE antibodies in patients with reliable histories of exposure to allergens.
- Intranasal corticosteroids are superior to other medications in achieving desired clinical outcomes, including quality of life.
- For some cases of allergic rhinitis, subcutaneous immunotherapy can achieve clinical remission for up to 3 years after cessation of therapy.
While allergic rhinitis is merely a nuisance to most people afflicted by it, the condition can lead to complications if it is severe or exists undetected for too long. In this article, I review the most reliable means of diagnosing allergic rhinitis, and outline a recommended approach to treatment.
Prevalence and pathophysiology
An estimated 20 to 40 million Americans are affected by allergic rhinitis. The actual prevalence of the condition is difficult to discern as many sufferers self-medicate without seeking medical care. One survey stated that up to 92% of patients had self-medicated prior to seeking medical care.1 Even when accounting for self-treatment, allergic rhinitis is the most commonly encountered form of chronic rhinitis, representing about 3% of all primary care office visits.2,3 Direct and indirect clinical costs run between $1.2 and $5.3 billion per year.4-6 Although the disease can develop in persons of any age, in 80% of cases symptoms will develop before the patient is 20 years old.5 Symptoms often wane as a patient grows older, and it is uncommon for persons older than 65 to experience new onset of allergic rhinitis.3,7
Allergic rhinitis stems from a type I hypersensitivity reaction.4 During an initial sensitization phase, the immune system identifies an allergen as foreign and generates specific antibodies to act against that allergen. Atopic patients exhibit an exaggerated response, generating high levels of Type 2 T-helper (Th2) cells and, subsequently, IgE antibodies.8 On reexposure to the allergen, specific IgE antibodies bound to mast cells form cross-links resulting in mast cell degranulation and the release of histamine and other chemical mediators. The patient then immediately develops such allergy symptoms as itching, sneezing, and rhinorrhea. A cellular inflammatory response, chiefly involving eosinophils, monocytes, and basophils, characterizes the secondary phase of the allergic reaction. Nasal congestion tends to dominate this later response phase.
Seasonal allergic rhinitis is usually triggered by pollens or molds. Perennial allergic rhinitis, triggered by dust mites, molds, cockroach or animal allergens, is defined as occurring 9 months out of the year.9
Clinical evaluation
The diagnosis of allergic rhinitis is usually made on the basis of the patient’s history and the results of your physical examination. In addition to classic symptoms of nasal congestion, itchy nose, sneezing, rhinorrhea, or itchy, watery eyes, patients may also complain of chronic cough, dry scratchy throat, otalgia, or recurrent sinusitis.4 Other important historical considerations include a family history of allergic rhinitis, a history of other atopic disease, previous treatment experiences, and suspected triggers.5
Physical clues to allergic rhinitis include boggy, pale, or “bluish” nasal turbinates, with watery discharge on nasal speculum exam. Patients may also have a nasal crease on the external nose caused by repeated rubbing or itching (the so-called “allergic salute”). Chronic nasal congestion may also precipitate darkening of the skin under the eyes or “allergic shiners.”2,6 Concurrent conjunctivitis is common. Polyps, seen on direct nasal examination, may occur both in allergic and non-allergic patients.
No studies have evaluated the accuracy of the history or physical examination in confirming the diagnosis of allergic rhinitis. The differential diagnosis is extensive and includes infectious rhinitis, non-allergic rhinitis with eosinophilia syndrome (NARES), occupational rhinitis, mechanical obstruction, vasomotor rhinitis, drug-induced rhinitis, and nasal polyps.5
Diagnostic tests
Published guidelines from the American Academy of Asthma, Allergy and Immunology, as well as other expert panels, recommend confirmatory testing when allergic rhinitis is clinically suspected.2,5,10 There is no evidence to support the superiority of this recommendation over an empiric trial of medication, and most primary care physicians choose to treat empirically based upon the history and physical examination.
Although further testing should be done when the diagnosis is unclear, be aware that there is uncertainty associated with allergy testing. Because an individual may become sensitized to an allergen without exhibiting symptoms of allergic rhinitis, there is no clearly defined reference standard for the confirmation of allergic rhinitis.11 Likewise, a history of sensitivity is not always followed by expected IgE test results. Challenge methods developed for studies of airborne allergens are used as reference standards in the evaluation of clinical tests.12