Urticaria

Rachelle L. Cassity

Urticaria (hives) is a common condition. The lesions appear well circumscribed. Typically, they are first erythematous and subsequently develop a central wheal. They usually clear within 3 to 4 hours, and the skin appears normal. It is estimated that at least 15% to 20% of the population will suffer one episode of hives during their lifetime. Urticaria occurs most frequently between the ages of 20 and 40 years, and more commonly in women than men.

Approach

Urticaria can be divided into two subcategories: acute and chronic. Acute urticaria is defined as intermittent or daily attacks that occur over a period of less than 6 weeks. If a urticaria attack lasts more than 6 weeks, it is classified as chronic (1).

A. Urticaria can also be classified as immunologic, nonimmunologic, or idiopathic.

1. Immunologic urticaria includes IgE-mediated hypersensitivity, complement-mediated hypersensitivity, and physical and contact urticaria.

2. Nonimmunologic urticaria includes mast cell release, physical agents, and contact urticaria.

3. Idiopathic

B. Special concerns. A severe urticarial reaction can be accompanied by angioedema and systemic symptoms. Also, urticarial vasculitis should be ruled out by skin biopsy if the lesions last longer than 24 hours.

History

A. Characteristics. Is the rash localized or systemic? Is it pruritic? What is the duration of symptoms? Does anything relieve the symptoms? Are there any specific triggers (2)?

1. Food and drugs are common causes of urticaria.

2. Certain systemic diseases can cause urticaria. Infections, connective tissue disorders, endocrine disorders, and neoplastic disorders are some examples.

3. Insect stings and bites are another common cause of urticaria.

B. Symptom chronology. When does it occur? How long does it last? Is it in association with physical trauma? Has the patient been on any medication that has helped relieve symptoms (e.g., antihistamines)?

C. Family history. Are there any members of the family who suffer from a connective tissue disorder? Do any complement disorders occur in the family, such as hereditary angioedema, which can be associated with urticaria? Also, is there a family history of atopy?

Physical examination

 A complete physical is required to rule out infection or other systemic diseases. An urticarial wheal is usually well demarcated. It begins as an erythematous area, which then develops a white center. The size of the wheal can vary from 2 mm to well over 30 cm. The rash is usually pruritic, especially when it occurs on the palms of the hand and the soles of the feet. Most often, the wheal will disappear within 3 to 4 hours of onset. The accompanying angioedema can last for a couple of days. The skin will return to normal once the wheal is gone.

Testing

 A. Laboratory tests. Routine tests include (a) complete blood count to look for eosinophilia, neoplastic disorders, and occult infection; (b) thyroid studies (thyroxine and thyroid-stimulating hormone; (c) erythrocyte sedimentation rate to help rule out connective tissue disorders and occult infection, urine analysis with urine culture, chemical profile, stool cultures for parasites, liver function tests, and an antinuclear antibody test. Other tests can include immunoglobulins, prick testing, rheumatoid factor, cryoglobulins, serum complement, and skin biopsy. However, laboratory tests often do not provide answers beyond those obtained in the history (3).

 B. Diagnostic imaging. Chest x-ray, sinus, and dental films may help to rule out cancer and infection.

Diagnostic assessment

It is important to rule out underlying conditions such as neoplastic disorders, endocrine disorders, connective tissue diseases, infections, and other disorders. The most significant factors in diagnosing acute urticaria are the history and physical examination. Facts must be obtained concerning food or drug ingestion, insect stings, current infections, or physical triggers such as cold or heat. Most acute urticarial reactions resolve spontaneously, but some continue and become chronic in nature. Of the chronic urticaria, a cause is found in only a few of these patients, with more than 75% of them having an idiopathic disorder (4).

References

1. Beltrani VS. Allergic dermatoses. Med Clin North Am 1998;82(5):1105–1133.

2. Greaves MW, Sabroe RA. ABC of allergies. Allergy and the skin. I—Urticaria. BMJ 1998;316(7138):1147–1150.

3. Kozel MM. The effectiveness of a history-based diagnostic approach in chronic urticaria and angioedema. Arch Dermatol 1998;134(12):1575–1580.

4. Greaves MW. Chronic urticaria [published erratum appears in N Engl J Med 1995;
333(16):1091]. N Engl J Med 1995;332(26):1767–1772.

Book Source Details

• Book Title: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter
• Author(s): Robert B. Taylor (editor)
• Year of Publication: 2000
• Copyright Details: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, Copyright © 2000 Lippincott Williams & Wilkins.

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More About This Book: Title: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter Authors: Robert B. Taylor (editor) Publisher: Lippincott Williams & Wilkins Copyright: 2000 ISBN: 0-78172-094-X

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