Urticaria (Hives)

Hives, or urticaria, is a skin condition characterised by red, raised, and itchy bumps. These bumps, or wheals, can appear anywhere on the body and may burn or sting. The rash can last from minutes to days without long-lasting skin changes. Less than 5% of cases last more than six weeks, a condition known as chronic urticaria. Hives often recur.

Signs and Symptoms

Hives appear as red, raised, itchy bumps that can burn or sting. They vary in size from pinpoint to several inches and can merge into larger areas. Individual hives last less than 24 hours and do not leave a bruise. Angioedema, a related condition, involves deeper swelling and can affect the lips, eyes, throat, and other areas.

Causes and Risk Factors

Hives can be triggered by various factors, including infections, allergic reactions to medications, insect bites, food, psychological stress, cold temperatures, and vibration. In about 50% of chronic cases, the cause remains unknown, often involving autoimmune reactions. Risk factors include hay fever and asthma.

Medications

Common drugs causing hives include antibiotics (penicillin), NSAIDs (ibuprofen), and antidiabetic drugs (glimepiride).

Food

Shellfish, nuts, eggs, wheat, and soy are common triggers. Balsam of Peru in processed foods and alpha-gal allergy causing sensitivity to red meat and milk are also notable.

Environmental Agents

Hives can be a symptom of parasitic infections like blastocystosis. Contact with plants like poison ivy can cause urushiol-induced contact dermatitis, often mistaken for hives.

Physical Factors

Dermatographic urticaria, seen in 4-5% of the population, is triggered by scratching or firm stroking of the skin. Pressure, cold, heat, sunlight, water, and exercise can also induce hives.

Pathophysiology

Hives result from histamine and inflammatory mediator release from mast cells, leading to fluid leakage from superficial blood vessels. This can occur via allergic (IgE-mediated) or nonallergic mechanisms, including direct histamine release by drugs or neuropeptide involvement in stress-induced hives.

Diagnosis

Diagnosis is primarily based on appearance and history. Acute urticaria resolves within six weeks, often due to identifiable triggers like food or infections. Chronic urticaria lasts longer and often has no identifiable cause. Patch testing and skin challenge tests may aid diagnosis, but extensive allergy testing is generally not recommended.

Treatment

Management involves education, avoiding triggers, and using antihistamines. Second-generation antihistamines (fexofenadine, loratadine, cetirizine) are preferred due to fewer side effects. For refractory cases, corticosteroids, leukotriene inhibitors, and immunosuppressants like omalizumab or cyclosporine may be used.

Systemic Steroids

Oral glucocorticoids are effective but have significant side effects and are recommended only for short-term use.

Leukotriene-Receptor Antagonists

Drugs like montelukast can be effective, especially for NSAID-induced urticaria.

Other Treatments

Anti-inflammatory medications (dapsone, sulfasalazine), monoclonal antibodies (omalizumab), and immunosuppressants (cyclosporine, tacrolimus) are options for severe, refractory cases.

Prognosis

Chronic urticaria affects quality of life and can be associated with psychiatric conditions like anxiety and depression. About 35% of people become symptom-free within a year, while others may experience persistent or recurrent symptoms.

Epidemiology

Chronic urticaria is more common in women and those over 40 years old, with a prevalence of 0.23% in the United States.

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Self-assessment MCQs (single best answer)

What is the medical term for hives?

Which of the following statements about hives is true?

What is the term for hives that last more than six weeks?

Which of the following is NOT a common trigger for hives?

What percentage of chronic urticaria cases have an unknown cause?

Which of the following is a common food trigger for hives?

What is the primary diagnostic method for hives?

Which medication is preferred for managing hives due to fewer side effects?

Which of the following is NOT a physical factor that can trigger hives?

Which age and gender are most commonly affected by chronic urticaria?