Urticaria

Urticaria or hives is a skin condition, commonly caused by an allergic reaction, that is characterized by raised red skin welts. It is also known as nettle rash or uredo. Welts from hives can appear anywhere on the body, including the face, lips, tongue, throat, and ears. Welts may vary in size from about 5 mm (0.2 inches) in diameter to the size of a dinner plate; they typically itch severely, sting, or burn, and often have a pale border. Urticaria is generally caused by direct contact with an allergenic substance, or an immune response to food or some other allergen, but can also appear for other reasons.