Alternative names :- Hay fever; Nasal allergies
An immune disorder, allergic rhinitis is a reaction to airborne (inhaled) allergens. Depending on the allergen, the resulting rhinitis and conjunctivitis may be seasonal (hay fever) or occur year round (perennial allergic rhinitis). Allergic rhinitis is the most common atopic allergic reaction, affecting over 20 million Americans. It's most prevalent in young children and adolescents but can Occur in all age-groups.
Hay fever reflects an immunoglobulin E (IgE)-mediated, Type I hypersensitivity response to an environmental antigen (allergen) in a genetically susceptible individual. In most cases, it's induced by wind-borne pollens: in the spring by tree pollens (oak, elm, maple, alder, birch, cottonwood); in the summer by grass pollens (crabgrass, bluegrass, fescue, and ryegrass); and in the fall by weed pollens (ragweed). Occasionally, hay fever is induced by allergy to fungal spores.
In perennial allergic rhinitis, inhaled allergens provoke antigen responses that produce recurring symptoms yearround.The major perennial allergens and irritants include dust mites, feather pillows, mold, cigarette smoke, upholstery, and animal dander's. Seasonal pollen allergy may exacerbate symptoms of perennial rhinitis.
Signs and symptoms
In seasonal allergic rhinitis, the key signs and symptoms are paroxysmal sneezing, profuse watery rhino, nasal obstruction or congestion, and priorities of the nose and eyes, usually accompanied by pale, cyanotic, edematous nasal mucous; red and edematous eyelids and conjunctivae; excessive acclimation; and headache or sinus pain. Some patients also complain of itching in the throat and malaise.
In perennial allergic rhinitis, conjunctivitis and other extra nasal effects are rare, but chronic nasal obstruction is common and often 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.
Some patients may develop chronic complications, including sinusitis and nasal polyps.
Microscopic examination of sputum and nasal secretions reveals large numbers of eosin. Blood chemistry studies show normal or elevated IE levels, possibly linked to seasonal overproduction of interleukin-4 and -5 (involved in the allergic inflammatory process). A firm diagnosis rests on the patient's personal and family history of allergies and on physical findings during a symtomatic phase. Skin testing, paired with tested responses to environmental stimuli, can pinpoint the responsible allergens when interpreted in light of the patient's history
To distinguish between allergic rhinitis and other disorders of the nasal mucosa, remember these differences:
Symptoms are controlled by eliminating the environmental antigen, if possible, and by drug therapy and immunotherapy.
Antihistamines and nasal decongestants are useful for treating acute symptoms. These drugs block histamine effects but commonly produce anticholinergic adverse effects (sedation, dry mouth, nausea, dizziness, blurred vision, and nervousness).
Newer antihistamines, such as cetirizine and loratadine, have proved effective in clinical trials. Fexofenadine, a derivative of terfenadine, may be effective but with less sedation and a lower risk of cardiac arrhythmias than terfenadine.
Inhaled intranasal steroids produce local anti-inflammatory effects with minimal systemic adverse effects. The most commonly used intranasal steroids are flunisolide and beclomethasone. These drugs usually aren't effective for acute exacerbations but can help control chronic symptoms.Advise the patient to use intranasal steroids regularly, as prescribed, for optimal effectiveness. Cromolyn sodium may be helpful in preventing allergic rhinitis. But this drug may take up to 4 weeks to produce a satisfactory effect and must be taken regularly during allergy season.
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. Local nasal immunotherapy is also being studied as an alternative route of allergen administration.
Most symptoms of allergic rhinitis can be readily treated.
In some cases (particularly children), people may outgrow an allergy as the immune system becomes less sensitive to the allergen. However, as a general rule, once a substance causes allergies for an individual, it can continue to affect the person over the long term.
More severe cases of allergic rhinitis require immunotherapy (allergy shots) or removal of tissue in the nose (e.g., nasal polyps) or sinuses.
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