Rhinitis is the most common manifestation of allergic disease, affecting 10 to 22% of adults and 10 to 42% of children.
Symptoms frequently become apparent during the first 5 years of life and may occur in a seasonal and/or perennial (year-round) pattern. Because sensitization to individual allergens requires repeated exposures, several seasons of exposure are necessary for the development of allergy to pollens or molds. This may explain why children with allergic rhinitis under the age of 5 years are typically sensitized to perennial indoor allergens, such as dust mites and animal danders, rather than seasonal allergens such as ragweed.
The symptom complex of allergic rhinoconjunctivitis results from the biochemical mediators elaborated during a type I (IgE-mediated) hypersensitivity reaction. Following the inhalation of aeroallergens into the nose, water-soluble antigens enter and diffuse through the mucous blanket that covers the respiratory tract mucosa. Interaction of these allergens with allergen-specific IgE on the surface of mast cells initiates cellular activation, culminating in the release of a multitude of preformed and newly synthesized bioactive molecules, including histamine and prostaglandin D2. These mediators produce symptoms shortly after allergen exposure and remit relatively quickly. However, symptoms frequently recur several hours later, coincident with a rise in many of the same mediators seen in the early response, along with a rise in cytokines (eg, IL-4 and IL-5) and the influx of helper T cells and eosinophils. This late allergic response is responsible for the inflammation seen in allergic rhinitis and contributes to the chronicity of the condition.
Nasal congestion is the most frequently reported symptom by patients with allergic rhinitis. Congestion resulting in near-total nasal obstruction may result in mouth breathing. Nasal pruritus may result in frequent wrinkling of the nose and/or rubbing of the nose with the heel of the hand, producing the allergic salute. Over time, this maneuver may lead to the formation of a transverse nasal crease. Pruritus of the palate, pharynx, and ears frequently accompanies nasal symptoms. Sneezing, often in paroxysms, is a common complaint, as is watery clear coryza. Postnasal drainage is a common problem and may result in worsening cough with recumbency. Uncomplicated allergic rhinitis is rarely associated with systemic pyrexia. Ocular symptoms may include excessive lacrimation and conjunctival injection.
Physical examination frequently discloses significant nasal congestion caused by edema of the mucosa overlying the nasal turbinates. The mucosa is pale with a blue hue and may appear redundant. In adolescents and adults, nasal polyps may be present. Polyps are uncommon in younger children, and their presence should suggest an alternative diagnosis, most often cystic fibrosis. The posterior oropharynx may have a cobblestoned appearance because of lymphoid hyperplasia. Edema of the nasal mucosa impedes venous return and results in infraorbital dark circles (allergic shiners) and periorbital edema. Additional wrinkles below the eyes (Dennie-Morgan lines) frequently accompany allergic shiners. Although these findings are common among children with allergic rhinitis, none are pathognomonic of the disorder.
The diagnostic evaluation of a patient with suspected allergic rhinitis may include examination of the nasal secretions for a predominance of eosinophils, which is suggestive, but not pathognomonic, of allergic rhinitis. Peripheral blood eosinophilia and elevated serum IgE levels are common, but nonspecific, findings. Testing for specific allergen sensitivities, by either skin testing or in vitro methods, should be interpreted in the context of the patient’s history in order to determine the clinical relevance of positive results.
The mucosal edema associated with allergic rhinitis is, in part, responsible for several complications of nasal allergy. Allergic inflammation may produce eustachian tube dysfunction and recurrent otitis media. Edema of the osteomeatal complex leads to impaired mucociliary clearance from the sinuses and contributes to the development of infectious sinusitis. Disturbances of olfaction and taste are quite bothersome to patients, as are interruptions of sleep by nasal obstruction and postnasal drainage. Prolonged mouth breathing may lead to disturbances in facial growth and dental malocclusion. Patients with allergic rhinitis have a higher incidence of bronchial hyperreactivity than patients without rhinitis and appear to be at increased risk for the subsequent development of asthma.
The approach to therapy in the patient with allergic rhinitis follows the treatment algorithm described above. Patient education focused on avoidance of allergens is central to the management of allergic rhinitis. Strict adherence to these principles may reduce symptoms, need for medications, and complications of rhinitis. Pharmacologic therapy is an adjunct to allergen avoidance. Antihistamines are the cornerstone of therapy for allergic rhinitis and are most effective for controlling sneezing, nasal and ocular pruritus, and coryza but provide less relief from nasal congestion.
If the combination of allergen avoidance and antihistamines does not adequately control symptoms, the addition of an antiinflammatory agent should be considered. Cromolyn sodium is available for both ocular and nasal administration and is most effective when administered before allergen exposure, such as before the onset of the spring pollen season, and continued throughout the time of exposure. Cromolyn has no appreciable side effects, but for maximal efficacy, it should be administered four to six times daily. For allergic conjunctivitis, two agents that possess both mast cellâ€“stabilizing properties and H1 receptor antagonist properties are lodoxamide and olopatadine. Topical nasal steroids are the most effective medication for all symptoms of allergic rhinitis and non-allergic rhinitis with eosinophilia syndrome (NARES). Agents currently available include pressurized metered dose inhalers or aqueous preparations of beclomethasone dipropionate, budesonide, flunisolide, fluticasone propionate, and triamcinolone. Once- or twice-daily administration is necessary for maximal efficacy. The most frequent adverse effects of these agents are local irritation and epistaxis. Concern surrounding the potential systemic effects of nasally applied steroids has discouraged their use in children. However, when administered at the lowest dose required to maintain their clinical effect, these agents rarely produce clinically significant side effects.