Clinical Definition

Urticaria, commonly called hives, is a vascular reaction to histamine in the upper dermis layers characterized by itching and patches of dermis that are redder than surrounding tissue.

In Our Own Words

Urticaria is commonly known as hives. Hives are itchy, raised, red splotches caused by a reaction to histamine, which the body produces as it fights allergens. Hives are red, especially at the edges, but may be paler in the center. They are usually short lived and commonly treated by avoiding the trigger and using antihistamines during a flare up. Hives may be part of an allergic spectrum that can involve more serious allergic illness, or it might just be hives, in the absence of other manifestations. For example, in a more serious reaction, a person can have hives and angioedema [link term], a reaction to histamine that goes deeper in the tissues and can compromise airflow. In rare cases, there may be a full-body allergic attack known as anaphylaxis.

There are many triggers for hives, including certain foods, medications or latex. Physical triggers, such as cold, sun exposure, sweating, pressure and vibration can also cause urticaria. In most cases, your doctor can help you identify (and avoid) your personal triggers.