Symptoms:

• Itching
• Swelling of the surface of the skin into red- or skin-colored welts (called wheals) with clearly defined edges

The welts may enlarge, spread, and join together to form larger areas of flat, raised skin. They can also change shape, disappear, and reappear within minutes or hours. The welts tend to start suddenly and resolve quickly. When you press the center of a red welt, it blanches (turns white).

Signs and tests:

Your doctor can tell if you have hives by the appearance of your skin. If you have a history of an allergy, then the diagnosis is even more obvious. Occasionally, skin or blood tests are performed to confirm that this was an allergic reaction and to test for the substance that caused your allergic response.