Hives -- what your doctor calls ''urticaria'' -- can be caused by allergic or other types of reactions. Hives appear as lesions on your skin. They’re usually very itchy and can last just a few minutes or several days before going away. Occasionally, however, these annoying blotches can be a sign of more serious problems, especially when someone has symptoms like trouble breathing.
Another reaction that sometimes happens along with hives is called angioedema. It’s swelling that develops under the skin. With angioedema, you may have deep swelling in such places as around the eyes and lips, and sometimes the genitals, hands, and feet.
In rare cases, the swelling from angioedema happens in the throat and causes trouble breathing. If that happens, you should call 911.
If you have hives along with fever, nausea, stomachcramps, shortness of breath, and a drop in blood pressure after a bee sting, insect bite, or drug injection, that can be a sign of a life-threatening allergy. Carry two epinephrine shots (such as Auvi-Q or Epi-Pen) if your doctor has prescribed them and use them if needed. Then call 911 or go to the hospital.
What Causes Hives?
Hives happen when some cells in the skin release a substance called histamine that triggers allergy symptoms.