The hives that appear cause considerable itching and can make a person extremely uncomfortable. The discomfort caused by hives can increase distress by making it difficult to sleep. When hives occur deeper in the skin and swelling occurs, this is called angioedema . The areas involved are usually the lips, eyelids, or genitals. Not all cases of hives cause angioedema.
Hives occur when fluid leaks through the cells surrounding tiny blood vessels and enters the skin.
This happens when a substance called histamine is released from a specialized type of cells, called mast cells, which lie along the blood vessels in the skin. Allergic reactions to foods or medications can cause the release of histamine by mast cells. In cases of acute urticaria, your child's dermatologist will try to identify the cause of the hives and eliminate it. If necessary, he or she may prescribe a mild antihistamine. Antihistamines stop the release of histamine from mast cells.