Introduction
Hives, also called urticaria, are itchy red bumps that appear on the skin and fade with pressure. They consist of dilated blood vessels and swelling near the skin surface. This same process can occur underneath the skin. This is called swelling or angioedema. Hives and swelling frequently occur together. About 40% of people with chronic urticaria have episodes of swelling. 10% of patients have swelling as their main symptom. Acute hives can occur for a short period of time from several hours to several days while chronic hives last continuously for 6 weeks or more. Acute hives occur in up to 20% of the population. At any time, up to 1% of the population may have chronic hives. About 20% the people with chronic hives have a physical trigger for their hives (e.g. pressure, scratching). This is termed physical urticaria. Chronic hives are more common in adults, especially women. Women are affected 2 times as often as mentioned. Chronic urticaria often begins in the third to fifth decade of life, though it can occur in any age group including infants. Chronic hives go into remission in many patients but the average duration is 2-5 years. Another name for chronic hives is chronic spontaneous urticaria.
Causes of hives
Acute hives are generally associated with a localized contact allergy (e.g. hives on the skin when sitting on the grass or with direct skin contact with animal) food allergy, drug, or infection. Hives from food usually occur immediately upon exposure and resolve within several hours. Acute hives, by definition are self-limited. Recent study showed that chronic hives, also called chronic spontaneous urticaria, rarely if ever have a primary external trigger. most cases are autoimmune, driven by an antibody and/or other factor within the body against an allergy cell in the skin called a MAST cell. When the MAST cells are stimulated, they release allergic mediators including histamine, that then go on to cause hives.
Workup and Treatment
Your BVAAC allergist will first take a comprehensive history, and perform a physical examination. In some cases, skin tests may be performed. Treatment consists of avoiding triggers including heat, physical factors, and in some cases NSAIDs. Medication consists of the use of non-sedating antihistamines such as cetirizine (Zyrtec), fexofenadine (Allegra), and loratadine (Claritin). Published guidelines strongly recommend increasing the dose of the non-sedating antihistamines up to a total of 4 pills per day (4 times the standard dose). Additional medicines that might be used would include sedating antihistamines like Benadryl at bedtime, montelukast, and Zantac, a medicine that blocks the H-2 receptor. In patients in whom high-dose antihistamines are ineffective, an injectable nonsteroidal biological medicines called Xolair may be used. This medication is given as an injection within the allergist’s office at a dose of 300 mg every 4 weeks. Xolair is very effective about 75% of the time in chronic spontaneous urticaria.
