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Urticaria is an inflammatory skin disorder caused by the abnormal release of inflammatory chemicals by cells of the immune system. In severe cases of urticaria, blood vessels can become inflamed. This condition is called urticarial vasculitis. This blood vessel inflammation causes skin redness, pain and itching sensations, and it also can cause systemic symptoms. This condition typically is treated with medications to reduce inflammation and to prevent the release of inflammatory chemicals.
Cells of the immune system known as mast cells product chemicals called histamines. When triggered by the presence of pathogens, mast cells release their histamines into the environment outside the cells, causing an inflammatory reaction. Sometimes, mast cells release their histamines in the absence of infection. This occurs in allergic reactions and in asthma, causing inflammation even though no infection has occurred. This mechanism also is responsible for the development of urticaria.
The reason why this reaction can lead to urticaria is unknown. This skin disorder generally is idiopathic, which means an underlying cause cannot be determined. Even so, there are some risk factors that can predispose certain people to developing the condition. These include viral diseases such as hepatitis and autoimmune disorders such as systemic lupus erythematosus. In addition, several medications, including angiotensin-converting enzyme (ACE) inhibitors, certain types of diuretics and penicillin, are risk factors.
Urticaria causes the formation of itchy skin lesions called erythematous wheals, which sometimes are called hives. These wheals typically are small, but larger wheals also can form. In severe cases of urticaria, the wheals might cover a large section of the back or chest as well as the limbs. If the skin inflammation spreads to blood vessels, urticarial vasculitis can develop, causing the wheals to become painful. If the skin wheals are itchy, the itching will tend to become more severe.
When blood vessels become inflamed, the skin lesions tend to change in appearance. Their pale red color intensifies while the center of the wheal remains pale. Petechiae, or small blood spots, might develop under the skin of the lesion. The lesions typically will begin to heal after approximately 24 hours. As the lesions heal, they turn darker in color before beginning to fade. People with a chronic form of urticarial vasculitis might experience multiple waves of lesions that last several months.
This skin disease sometimes causes systemic symptoms in addition to skin lesions. Systemic symptoms might include swollen lymph nodes, joint pain, fever and sensitivity to light. Some people might also have some abdominal pain or have difficulty breathing. More serious symptoms are rare, but can include kidney or lung problems. For this reason, medical advice should be sought if any systemic symptoms are experienced.
Urticarial vasculitis is a non-fatal disease, but for some people, it is a lifelong condition. Treatment might be required for months or even years before lesion formation can be controlled. The most common form of treatment for people with a mild form of the disease is antihistamine medication to reduce the release of histamines by mast cells. Non-steroidal anti-inflammatory medications are prescribed to reduce inflammation. People with chronic or severe urticarial vasculitis might be given a short course of steroids, which will suppress the inflammation and sometimes will induce remission.