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Urticaria, Angioedema and Anaphylaxis

Urticaria, angioedema, and anaphylaxis are manifestations of the immediate hypersensitivity reaction. Immediate hypersensitivity is an antibody mediated reaction that occurs within minutes to hours of exposure to a particular antigen by an immune individual. Twenty percent of the population will have one of these manifestations, especially urticaria.


Treatment of Urticaria, Angioedema and Anaphylaxis

Urticaria (or hives) is an intensely itchy rash that consists of raised, irregularly shaped wheals. The wheals have a blanched center, surrounded by a red flare. Urticaria is caused by histamine release from dermal mast cells. Histamine release is most commonly caused by an immunologic reaction between antigens and IgE antibodies bound to mast cell membranes. Histamine causes increased vascular permeability. Antigens, chemicals and physical agents (detergents or ultraviolet light) can cause urticaria.

Angioedema is an area of circumscribed swelling of any part of the body. It may be caused by the same mechanisms that cause hives except that the immunologic events occur deeper in the cutis or in the submucosal tissue of the respiratory.

Anaphylaxis is the acute reaction that occurs when an antigen is introduced systemically into an individual who has preexisting IgE antibodies.

The patient has difficulty breathing from constriction of the major airways and shock due to falling blood pressure. The reaction occurs within seconds an hour of introduction of the antigen.

An anaphylactoid reaction is similar to anaphylaxis, but it is not immunologically mediated. Mannitol, radiocontrast material, and drugs (opiates, vancomycin) may degranulate mast cells.


Common causes of IgE-mediated anaphylaxis

Insect venoms

Airborne allergens

Foods such as peanuts, eggs, milk, sea foods, and food dyes and flavors

Antitoxins to tetanus and other microbial products of animal origin

Low molecular weight chemicals may bind to host proteins and act as haptens in the production of IgE antibodies. These low molecular weight chemicals, such as drugs (particularly penicillins), are not in themselves immunogenic.

Symptoms of anaphylaxis include pruritus, injection of the mucous membranes, bronchospasm, and hypotension.

Prevention of Anaphylaxis

Anaphylaxis is best prevented by avoidance of the cause. However, anaphylaxis frequently is unanticipated. Individuals with a history of anaphylaxis should be provided with injectable epinephrine.

Short-term desensitization may be needed in a patient requiring antibiotic treatment. Desensitization is accomplished by injecting increasing doses of penicillin, every 20 minutes, over 8 hours, starting with 10 units and increasing to 1,000,000 units.

Long-term desensitization has a 90% success rate with bee venom and a 85% success rate for rhinitis due to inhalants. Desensitization to food allergens is very hazardous and should not be attempted.

Treatment of Acute Anaphylaxis

Epinephrine in a 1:1000 dilution (1.0 mg/mL) should be injected at 10-20 min intervals at 0.01 mL/kg SQ per dose, with a maximum dose of 0.3 mL/kg per dose SQ.

Oxygen should be administered (100%, 4-6 L/min) and the airway secured.

Albuterol, 0.1-0.2 mL/kg in a 5 mg/mL solution, should be given via nebulizer every 4-6 hours.

Administration of diphenhydramine or chlorpheniramine and corticosteroids are secondary measures which


Hives most commonly urticaria, angioedema, anaphylaxis, allergy, hives, wheezing results from ingestion of foods, food additives, or drugs. These usually cause hive formation for only a few hours to two days. Hives also may be associated with infections caused by parasites or viruses (eg, hepatitis or infectious mononucleosis). Hives may also occur in collagen vascular diseases, such as systemic lupus erythematosus.

Cold urticaria may be induced by exposure to

Cholinergic urticaria is characterized by the appearance of small punctate wheals, surrounded by a prominent erythematous flare. These small papularurtications are pruritic and appear predominantly on the neck and upper thorax. The lesions often develop after exercise, sweating, exposure to heat, or anxiety. This type of urticaria is caused by stimulation of cholinergic fibers. Cholinergic urticaria is treated with hydroxyzine in a dose of 50-100 mg/day. Prophylactic treatment consists of hydroxyzine

Chronic urticaria is caused by ingestion of food substances that contain natural salicylates. Sensitivity to the food additive tartrazine yellow No. 5 frequently is found in patients with salicylate sensitivity. Chronic urticaria is treated with corticosteroids.

Exercise urticaria is characterized by hives and bronchospasm after exercise. Sometimes the recent ingestion of an offending food in combination with exercise will cause symptoms of immediate hypersensitivity.

Genetic deficiencies of complement factor H or factor I may cause urticaria. Patients who have these defects frequently develop severe hives, particularly after exposure to cold or hot water or alcohol ingestion. These rare defects are inherited as autosomal recessive traits.

The diagnosis is made by finding a low level of serum C3.

Treatment consists of nonsedating antihistamines such as loratadine or fexofenadine.

Treatment of Urticaria. Urticaria generally is a self-limiting disorder and usually requires only

IV. Angioedema