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Hives, also known as urticaria, develop when histamine is released by mast cells; this causes blood vessels to leak and hives to break out. Allergic reactions also involve histamine, which is why people often associate hives with allergic responses to food, medicine and environmental stimulants. There are other causes of hives, though, including additional triggers in the environment, illness and stress. In many cases, the cause of an outbreak is unknown.
When a person has hives, he or she suddenly develops pink or red bumps and welts on the skin. These areas of raised skin vary in size and can occur anywhere. Deeper swelling in the skin is known as angioedema, a condition that affects the face as well as the hands and feet. Angioedema is related to hives but can also be genetic. Dermatographia, also known as skin writing, can occur with hives and is a condition in which a scratch can cause the scratched skin to rise.
In ordinary hives, the cause is often undetermined. With physical hives, physical exposure to and contact with stimulants such as sunlight and water are said to be the cause. Both ordinary and physical hives can be acute or chronic.
An outbreak that suddenly appears and disappears within six weeks is known as acute hives. Commonly, causes of hives that are acute are allergic reactions or infections. Chronic hives remain longer than six weeks and can even last for years. Causes of hives that are chronic are harder to pinpoint since medical tests often do not provide many, if any, answers.
Since causes of hives vary and are sometimes unknown, treatment options do not necessarily cure the condition; rather, they are used to ease uncomfortable symptoms while waiting for the hives to clear up. Antihistamines help counteract histamine release in the body and work to prevent more hives from forming. To reduce itching and swelling, topical creams can be used. Careful consideration to simple habits like not wearing tight clothes or not taking hot showers also help in lessening the itching. Severe symptoms might require an epinephrine or steroid injection.
Hives tend to be itchy and sometimes sting or burn, and just as suddenly as they appear, they can disappear. When hives emerge in different areas after disappearing in others, it gives the appearance that the condition moves around. Although hives can look more serious than they really are, severe cases can cause lightheadedness and breathing or swallowing difficulties. In this event, the afflicted person would require treatment in an emergency room.