Urticaria affects up to 25% of people at some point in their lives. Up to 3% of people have chronic idiopathic urticaria, which means that the urticaria has been occurring for more than 6 weeks, and has no identifiable cause.
There are a number of possible triggers of urticaria, but 80-90% of cases of chronic urticaria (urticaria that has been occurring for at least 6 weeks) are idiopathic, which means that there is no identifiable trigger. In cases that do have a trigger, there are a number of possible triggers: foods, medications, infections (viral, and possibly bacterial or fungal), other chronic medical illnesses (such as lupus, thyroid disease, and even cancer), heat, cold, pressure to the skin, trauma to the skin, sun exposure, water, and exercise, among others.
A number of recent studies have found that as many as 40-60% of people with chronic idiopathic urticaria have an autoimmune cause of their urticaria. When a part of the patient’s own blood is injected into the top layer of his/her skin, a hive occurs, suggesting that there is something in the patient’s own blood that can cause a hive to occur in the skin. Further studies have found that some of these patients have antibodies that bind to receptors on some of the skin cells. These antibodies probably trigger the cells to release histamine, which causes a hive. There are no commercially available tests to find out if a patient has autoimmune urticaria, but the tests can be done on an experimental basis at certain research centers. We do not currently know of any easy way to get rid of these antibodies, so for now, these patients are treated in the same way as any other patient with chronic idiopathic urticaria. However, future research may lead to the discovery of a new way to treat these patients who have autoimmune antibodies that cause urticaria.
In cases where a trigger can be identified, the best way to treat the urticaria is by avoidance of the trigger. In cases where no trigger can be identified (80-90% of long-standing urticaria), there are some medications which can help to relieve, and even prevent symptoms. Antihistamines are the most helpful. Over-the-counter antihistamines, such as Benadryl, are helpful, but often cause side-effects, such as drowsiness. Some of the newer prescription antihistamines can help without causing any side-effects. Some cases might require a short course or a shot of steroid medication, but long-term treatment with steroids is usually avoided because of possible harmful side-effects. However, in severe cases that do not respond to the usual medicines, long-term treatment with low doses of steroids can be considered. Some of the disease modifying drugs that are used for connective tissue diseases (such as lupus and rheumatoid arthritis) have been found to be helpful in some patients with severe chronic urticaria, but these drugs are frequently associated with side effects. There is currently no known way to permanently cure chronic idiopathic urticaria (long-standing urticaria without any identifiable trigger), but we do know that most cases are characterized by periodic flare-ups with symptom-free intervals in between, and most of the time the urticaria will eventually “burn out” and never come back, although this may not happen until many months or even years have gone by.
*Adapted from Urticaria.net