Urticaria, or hives, is a common problem seen in doctors’ offices. In some patients, in addition to hives, there may also be swelling of the lips or throat. This is called angioedema. The cause of the hives and angioedema is most likely degranulation of mast cells. Everyone has mast cells on the exposed parts of the body. Theses mast cells are loaded with histamine, leukotrienes, and several other chemicals. If these chemicals stay inside the mast cells, they do not cause any problems. Once they are released, the open up the blood vessels and create inflammation.
Introduction to Urticaria
An inflammatory reaction in the outer layers of the skin is a hive. An inflammatory reaction in the deeper layers of the skin or in the GI Tract is angioedema. The question everybody asks is what makes these mast cells degranulate. The most common cause is an allergic reaction. However, these hives are acute and usually last no more than a few days. We can do skin testing and identify the allergen in these situations.
However, in chronic urticaria, infective agents like viral antigens may be the cause for the degranulation of the mast cells. These hives can last for weeks and sometimes for months.
Some physical factors like exposure to the cold and physical pressure can also degranulate mast cells. More common in this group is dermographism, but most of these hives have a “streaky” appearance.
Some medications such as morphine and codeine, and histamine-containing foods such as chocolate and eggplant, can also degranulate the mast cells. In some instances, we cannot find the causative agent (idiopathic urticaria). In occasional instances, malignant cells acting as a foreign antigen can also degranulate mast cells, but this is very unusual. Viruses and connective tissue disorders, even sinusitis can cause chronic urticaria & angioedema. The majority of cases, however, have no underlying disease and will resolve in time.
In acute reactions, giving epinephrine, a short course of oral steroids, and antihistamines are indicated. In chronic hives, the usual treatment is a long-acting antihistamine along with short-acting antihistamines and also using an H2 blocker like Tagamet on a regular basis for a few weeks and possibly a short course of oral steroids.
In spite of these treatments, some patients have chronic hives for months or years. In these instances, we do blood work and a chest x-ray to rule out any other illnesses that may cause these hives.
What are the different types of urticaria?
They can be classified into two categories: Immunologic and Non-Immunologic. Allergic or Immunologic Urticaria is the least common form. It is caused by the immune system’s overreaction to foods, drugs, infection insects stings, blood transfusions or other substances. Foods such as eggs, nuts and shellfish, and drugs such as penicillin and sulfa are common causes of allergic or immunologic urticaria.
Non-Immunologic Urticaria are those types of urticaria where a clear-cut allergic basis cannot be proven. These take many forms. Dermographism is urticaria that develops when the skin is stroked with a firm object. Cold-Induced Urticaria appears after a person is exposed to low temperatures-for example, after a plunge into a swimming pool or when an ice cube is placed against the skin. Cholinergic Urticaria, which is associated with exercise, hot showers and/or anxiety, is a form of hives that is related to release of certain chemicals from parts of the nervous system that control such body functions as blood pressure and heart rate. Pressure Urticaria develops from the constant pressure of constricting clothing such as sock bands, bra straps, belts or other tight clothing. Solar Urticaria arises on parts of the body exposed to the sun: This may occur within a few minutes after exposure. Some cases of non-immunologic urticaria may be caused by non-allergic reactions to aspirin and possibly, certain food dyes, sulfites, and other food additives. In many cases, particularly in chronic urticaria, the trigger for the problem can’t be found; in this instance it is called Idiopathic Urticaria.
How is urticaria treated?
Your allergist first will alleviate the discomfort with medications; for example, antihistamines. Severe attacks of urticaria can be temporarily relieved by injections of epinephrine; rarely in these cases corticosteroids may be prescribed for a short period. Other drugs may be required for specific types of urticaria.
Of course, if the cause can be identified, the best course of treatment is avoidance of the substance that triggers urticaria. If a problem with a specific food is strongly suspected, then is should be avoided. This may require a careful reading of packaged food labels and inquiry about ingredients in restaurant meals. Persons with Solar Urticaria should wear protective clothing and apply sunscreen lotions when outdoors. Loose-fitting clothing will help relieve Pressure Urticaria. Avoid harsh soaps and frequent bathing to reduce the problem of dry skin, which can cause itching and scratching that can aggravate urticaria. Vigorous toweling after a bath may precipitate hives. Although success of identifying the cause of chronic urticaria varies from clinic to clinic according to patient populations, it usually is no higher than 20% of cases. It may last for months or for years and burn itself out, never to bother the sufferer again.