Hives: Overview Hives What are hives?This is a skin reaction that causes bumps, raised patches, or both to suddenly appear on the skin. The bumps and raised patches are often itchy and may look swollen. The medical name for hives is urticaria. Are hives contagious?No, you cannot get hives by

  Rash from poison ivy. Many people develop an itchy rash that causes lines or streaks that look like this. Poison ivy, oak and sumac: Overview Many people get a rash from poison ivy, poison oak, and poison sumac. This rash is caused by an oil found in the plants. This oil is called urushiol (you-ROO-shee-all).