Urticaria [Hives]
Urticaria [Hives]: Excerpt from Professional Guide to Signs & Symptoms (Fifth Edition)
Urticaria is a vascular skin reaction characterized by the eruption of transient pruritic wheals—smooth, slightly elevated patches with well-defined erythematous margins and pale centers of various shapes and sizes. This reaction is caused by the local release of histamine or other vasoactive substances as part of a hypersensitivity reaction. (See Recognizing common skin lesions, pages 590 and 591.)
Acute urticaria evolves rapidly and usually has a detectable cause, such as hypersensitivity to certain drugs, foods, insect bites, inhalants, or contactants; emotional stress; or environmental factors. Although individual lesions usually subside within 12 to 24 hours, new crops of lesions may erupt continuously, thus prolonging the attack.
Urticaria lasting longer than 6 weeks is classified as chronic. The lesions may recur for months or years, and the underlying cause is usually unknown. Occasionally, a diagnosis of psychogenic urticaria is made.
Angioedema, or giant urticaria, is characterized by the acute eruption of wheals involving the mucous membranes and occasionally the arms, legs, or genitalia.
Emergency Interventions
In a patient with acute urticaria, quickly evaluate his respiratory status and take his vital signs. Ensure patent I.V. access if you note respiratory difficulty or signs of impending anaphylactic shock. Also, as appropriate, give local epinephrine or apply ice to the affected site to decrease absorption of the irritating agent through vasoconstriction. Clear and maintain the airway, give oxygen as needed, and institute cardiac monitoring. Have resuscitation equipment at hand, and be prepared to begin cardiopulmonary resuscitation. Intubation or a tracheostomy may be required.
History
If the patient isn’t in distress, obtain a complete history. Does he have any known allergies? Does the urticaria follow a seasonal pattern? Do certain foods or drugs seem to aggravate it? Is it related to physical exertion? Is the patient routinely exposed to chemicals on the job or at home? Has he recently used new skin products? Obtain a detailed drug history, including prescription and over-the-counter drugs. Note any history of chronic or parasitic infection, skin disease, or a GI disorder.
Medical causes
Anaphylaxis
This life-threatening reaction is marked by the rapid eruption of diffuse urticaria and angioedema, with wheals ranging from pinpoint to palm-size or larger. Lesions are usually pruritic and stinging and preceded by paresthesia. Other acute findings include profound anxiety, weakness, diaphoresis, sneezing, shortness of breath, profuse rhinorrhea, nasal congestion, dysphagia, and warm, moist skin.
Lyme disease
Urticaria may result from the characteristic skin lesion (erythema chronicum migrans) produced by this tick-borne disease. Later effects include constant malaise and fatigue, intermittent headache, fever, chills, lymphadenopathy, neurologic and cardiac abnormalities, and arthritis.
Other causes
Drugs
Many drugs can produce urticaria. Among the most common are aspirin, atropine, codeine, dextrans, immune serums, insulin, morphine, penicillin, quinine, sulfonamides, and vaccines. In addition, radiographic contrast media commonly produce urticaria, especially when administered I.V.
Special considerations
To help relieve the patient’s discomfort, apply a bland skin emollient or one containing menthol and phenol. Expect to give an antihistamine, a systemic corticosteroid or, if stress is a suspected contributing factor, a tranquilizer. Tepid baths and cool compresses may also enhance vasoconstriction and decrease pruritus. Advise the patient to avoid the causative stimulus if it’s identified.
Pediatric pointers
Pediatric forms of urticaria include acute papular urticaria (usually after insect bites) and urticaria pigmentosa (rare).
Book Source Details
- Book Title: Professional Guide to Signs & Symptoms (Fifth Edition)
- Author(s): Springhouse
- Year of Publication: 2006
- Copyright Details: Professional Guide to Signs & Symptoms (Fifth Edition), Copyright © 2006 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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