Hives, also known as urticaria, are welts on the skin that often itch. Typically, they do not persist for more than 24 hours. If a bout of hives last less than 6 weeks, it is called acute urticaria. If they linger for more than 6 weeks, they are classified as chronic.
In acute urticaria, an underlying cause can be usually identified and eliminated. Things that most commonly trigger urticaria include:
- Food (especially peanuts, eggs, nuts and shellfish)
- Medications, such as antibiotics (especially penicillin and sulfa), aspirin and ibuprofen
- Insect stings or bites
- Physical stimuli, such as pressure, cold, heat, exercise or sun exposure
- Blood transfusions
- Bacterial infections, including urinary tract infections and strep throat
- Viral infections, including the common cold, infectious mononucleosis and hepatitis
- Pet dander
- Pollen and some plants, such as poison oak and poison ivy
In the setting of chronic urticaria, the cause is usually more difficult to identify and often requires extensive blood work.
Management of urticaria begins with elimination of suspected causes. Blood work and allergy testing may be necessary. To control the symptoms, antihistamines are often prescribed. Severe cases associated with difficulty breathing or swallowing can be life threatening and should be managed in an emergency room setting.