diagnostic chemicals such as radiographic contrast media foods such as nuts and

Diagnostic chemicals such as radiographic contrast

This preview shows page 355 - 357 out of 540 pages.

diagnostic chemicals such as radiographic contrast media foods, such as nuts and seafood sulfite-containing food additives insect venom, such as that from honeybees, wasps, and certain spiders 345 IMMUNE DISORDERS Treatment of allergic rhinitis involves controlling signs and symptoms and preventing infection. Treatment may include re- moving the environmental allergen. Drug therapy and immu- notherapy may be used to treat perennial allergic rhinitis. Annoying aftereffects Antihistamines, such as chlorpheniramine, diphenhydramine, and promethazine, are effective in stopping a runny nose and watery eyes, but they usually produce sedation, dry mouth, nausea, dizziness, blurred vision, and nervousness. Nonsedat- ing antihistamines, such as loratadine, desloratadine, fexofena- dine, and cetirizine, produce fewer annoying effects and have emerged as the treatment of choice. Try these treatments, too Topical intranasal corticosteroids may reduce local inflamma- tion with minimal systemic adverse effects. Cromolyn sodium may help prevent allergic rhinitis, but it takes 4 weeks to pro- duce a satisfactory effect and must be taken regularly during allergy season. Long-term management may include immunotherapy or de- sensitization with injections of allergen extracts administered preseasonally, seasonally, or every year. Battling illness Treating allergic rhinitis Anaphylaxis can result from contact with many common substances.
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a ruptured hydatid cyst (rare). Penicillin is the most common anaphylaxis-causing antigen. It induces a reaction in 4 out of every 10,000 patients. Reenacting the reaction Here’s how an anaphylactic reaction occurs: After initial exposure to an antigen, the immune system re- sponds by producing IgE antibodies in the lymph nodes. Helper T cells enhance the process. Antibodies bind to membrane receptors located on mast cells in connective tissues and on basophils, which are a type of leuko- cyte. On reexposure, the antigen binds to adjacent IgE antibodies or cross-linked IgE receptors, activating inflammatory reactions such as the release of histamine. Untreated anaphylaxis causes respiratory obstruction, sys- temic vascular collapse, and death—minutes to hours after the first symptoms occur. However, a delayed or persistent reaction may last up to 24 hours. (See Treating anaphylaxis and Under- standing anaphylaxis .) 346 IMMUNE SYSTEM Anaphylaxis is always an emergency. It re- quires an immediate injection of epinephrine 1:1,000 aqueous solution, 0.1 to 0.5 ml, subcuta- neously (subQ) or I.M. If signs and symptoms persist, the injection should be repeated at 10- to 15-minute intervals as needed. Alternatively, 0.1 to 0.25 mg (1 to 2.5 ml of a 1:10,000 solution) may be given I.V. slowly over 5 to 10 minutes. The I.V. dose may be repeated every 5 to 15 minutes if needed or followed by an infusion at 1 to 4 mcg/minute. Diphenhydramine (Bena- dryl), 50 mg I.M. or I.V., may be given for aller- gic signs and symptoms. Aminophylline helps relieve bronchospasm.
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