Angioedema

Urticaria, commonly called hives, is an inflammation of the surface layers of the skin, and is characterized by small, itchy red or white welts (called wheals). Urticaria is usually caused by an allergic reaction; however, the allergenic trigger is often unknown. When a cause can be identified, it is frequently something taken by mouth, such as shellfish or other fish, dairy products, peanuts or other legumes, chocolate, fresh fruit, or medications. Sometimes other allergens such as pollens, molds, or animal dander can produce hives. Hives can also be caused by heat (cholinergic urticaria or "prickly heat"), cold (cold urticaria), pressure (dermographism and pressure urticaria), light (solar urticaria), exercise, and certain infections such as hepatitis B.
In most acute cases, urticaria disappears within hours or days without any treatment. Sometimes, however, it may continue for a prolonged period, or recur frequently. Such chronic cases are often very difficult to treat.
Urticaria is closely related to another condition called angioedema, which involves swelling in the deeper layers of the skin. When swelling occurs in the throat or tongue, angioedema can be life-threatening.
Urticaria and angioedema are also closely related to anaphylaxis, an extremely dangerous condition that can lead to death within minutes or hours. Anaphylaxis is an overwhelming allergic reaction that may lead to swelling of internal organs, collapse of blood circulation, shock, or suffocation. It may be caused by all the same factors that trigger hives; one of the most well-known causes is bee sting allergy. (See also Food Allergies.)
Conventional treatments for urticaria and angioedema include avoidance of triggering factors, antihistamines, and, occasionally, corticosteroids. When breathing is threatened, epinephrine shots and possibly hospitalization may be needed.

Proposed Treatments:
Elimination Diet
Because urticaria is frequently caused by allergens in food, the so-called elimination diet has been tried as a treatment for chronic symptoms.
There are many forms of the elimination diet. One of the most common involves starting with a highly restricted diet consisting only of foods that are seldom allergenic, such as rice, yams, and turkey. Other proponents of the elimination diet allow a greater range of foods at the outset. If dietary restriction leads to resolution or improvement of symptoms, foods are then reintroduced one by one to see which, if any, will trigger urticaria. (For more information see the article on food allergies.)
The results of preliminary studies suggest that the elimination diet can be effective in some cases of chronic or recurrent urticaria. However, it is an arduous approach that is not for the faint of heart. Various forms of allergy testing have been advocated to make matters easier; the idea is to identify specific offending foods only, rather than eliminating practically everything. Unfortunately, food allergy testing appears to be somewhat unreliable.
Acupuncture
In China, urticaria is often treated with acupuncture; however, the evidence that acupuncture works for this condition is very weak.
Other Natural Treatments
Vitamins C and B12, and the flavonoid quercetin, have also been suggested, but there is no evidence as yet that they really work for treating urticaria.