Hives are sharply marginated, red, raised areas that involve the superficial portion of the skin. When swelling extends into the deeper layer of the skin or soft tissue, it is known as angioedema. Hives frequently cause severe itching. Angioedema can occur in the upper airway causing difficulty breathing.

Causes of hives and angioedema are allergies (foods, drugs, inhalants, contactants), infection, insect bite, collagen vascular diseases (Lupus, etc.), certain malignancies, physical urticaria (cold urticaria, solar urticaria, etc.) and certain hereditary conditions. In 85% of chronic cases, the exact cause is unknown (physicians refer to this situation as Chronic Idiopathic Urticaria).

Whenever a provoking factor can be identified, avoidance is recommended. The first step of medical treatment is antihistamines (H-1 blockers). In general, long-acting, non-sedating antihistamines are recommended. At bedtime, Benadryl or hydroxyzine can be added. If H-1 blockers alone are not enough, H-2 blockers such as cimetidine (Tagamet) should be added. Studies have shown that an H-1 blocker plus an H-2 blocker work better than an H-1 blocker alone. Systemic corticosteroids are effective but should be avoided as much as possible because of side effects. Angioedema in the throat can be life threatening because it can cut off airflow - Epinephrine (adrenaline) injection is indicated in this situation. Epinephrine is available as a self-injection (Epi-Pen Kit). People who have chronic angioedema should always carry Epi-Pen.