Allergic rhinitis
Allergic rhinitis: Excerpt from Professional Guide to Diseases (Eighth Edition)
Allergic rhinitis is a reaction to airborne (inhaled) allergens. Depending on the allergen, the resulting rhinitis and conjunctivitis may occur seasonally (hay fever) or year-round (perennial allergic rhinitis).
Causes and incidence
Hay fever reflects an immunoglobulin (Ig) E-mediated type I hypersensitivity response to an environmental antigen (allergen) in a genetically susceptible individual. In most cases, it’s induced by windborne pollens: in the spring by tree pollens (oak, elm, maple, alder, birch, and cottonwood), in the summer by grass pollens (sheep sorrel and English plantain), and in the fall by weed pollens (ragweed). Occasionally, hay fever is induced by allergy to fungal spores. In addition to individual sensitivity and geographical differences in plant population, the amount of pollen in the air can be a factor in determining whether symptoms develop. Hot, dry, windy days have more pollen than cool, damp, rainy days.
In perennial allergic rhinitis, inhaled allergens provoke antigen responses that produce recurring symptoms year-round. The allergens trigger antibody production and histamine release, producing itching, swelling, and mucus. The major perennial allergens and irritants include dust mites, feather pillows, mold, cigarette smoke, upholstery, and animal dander. Seasonal pollen allergy may exacerbate signs and symptoms of perennial rhinitis.
Allergic rhinitis is the most common atopic allergic reaction, affecting more than 20 million Americans. It’s most prevalent in young children and adolescents but can occur in all age groups.
Signs and symptoms
In seasonal allergic rhinitis, the key signs and symptoms are paroxysmal sneezing, profuse watery rhinorrhea, nasal obstruction or congestion, and pruritus of the nose and eyes. It’s usually accompanied by pale, cyanotic, edematous nasal mucosa; red and edematous eyelids and conjunctivae; excessive lacrimation; and headache or sinus pain. Some patients also complain of itching in the throat and malaise.
In perennial allergic rhinitis, conjunctivitis and other extranasal effects are rare, but chronic nasal obstruction is common. In many cases, this obstruction extends to eustachian tube obstruction, particularly in children.
In both types of allergic rhinitis, dark circles may appear under the patient’s eyes (“allergic shiners”) because of venous congestion in the maxillary sinuses. The severity of signs and symptoms may vary from season to season and from year to year.
Diagnosis
Microscopic examination of sputum and nasal secretions reveals large numbers of eosinophils. Blood chemistry shows normal or elevated IgE. A definitive diagnosis is based on the patient’s personal and family history of allergies as well as physical findings during a symptomatic phase. Skin testing paired with tested responses to environmental stimuli can pinpoint the responsible allergens given the patient’s history. In patients who can’t tolerate skin testing, the radioallergosorbent test may be helpful in determining specific allergen sensitivity.
To distinguish between allergic rhinitis and other nasal mucosa disorders, remember these differences:
❑ In chronic vasomotor rhinitis, eye symptoms are absent, rhinorrhea is mucoid, and seasonal variation is absent.
❑ In infectious rhinitis (the common cold), the nasal mucosa is beet red; nasal secretions contain polymorphonuclear, not eosinophilic, exudate; and signs and symptoms include fever and sore throat. This condition isn’t a recurrent seasonal phenomenon.
❑ In rhinitis medicamentosa, which results from excessive use of nasal sprays or drops, nasal drainage and mucosal redness and swelling disappear when such medication is withheld.
❑ In children, differential diagnosis should rule out a nasal foreign body, such as a bean or a button.
Treatment
Treatment aims to control symptoms by eliminating the environmental antigen, if possible, and providing drug therapy and immunotherapy.
Antihistamines block histamine effects but commonly produce anticholinergic adverse effects (sedation, dry mouth, nausea, dizziness, blurred vision, and nervousness). Antihistamines, such as cetirizine, loratadine, and fexofenadine, produce fewer adverse effects and are less likely to cause sedation.
Inhaled intranasal steroids produce local anti-inflammatory effects with minimal systemic adverse effects. The most commonly used intranasal steroids are fluticasone, mometasone, and triamcinolone. These drugs are effective when symptoms aren’t relieved by antihistamines alone.
Advise the patient to use intranasal steroids regularly as prescribed for optimal effectiveness. Cromolyn may be helpful in treating hay fever, but this drug may take up to 4 weeks to produce a satisfactory effect and must be taken regularly during allergy season. Eye drop versions of cromolyn and antihistamines are available for itchy, bloodshot eyes.
Long-term management includes immunotherapy, or desensitization with injections of extracted allergens, administered before or during allergy season or perennially. Seasonal allergies require particularly close dosage regulation.
Special considerations
❑ Before desensitization injections, assess the patient’s symptom status. Afterward, watch for adverse reactions, including anaphylaxis and severe localized erythema.
❑ Keep epinephrine and emergency resuscitation equipment available, and observe the patient for 30 minutes after the injection. Instruct the patient to call the physician if a delayed reaction should occur.
The following protocol is recommended for allergic rhinitis:
❑ Monitor the patient’s compliance with prescribed drug treatment regimens. Also carefully note any changes in the control of his symptoms or any signs of drug misuse.
❑ To reduce environmental exposure to airborne allergens, suggest that the patient sleep with the windows closed, avoid the countryside during pollination seasons, use air conditioning to filter allergens and minimize moisture and dust, and eliminate dust-collecting items, such as wool blankets, deep-pile carpets, and heavy drapes, from the home.
❑ In severe and resistant cases, suggest that the patient consider drastic changes in lifestyle such as relocation to a pollen-free area either seasonally or year-round.
❑ Be aware that some patients may develop chronic complications, including sinusitis and nasal polyps.
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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