Hives are localized, raised red areas in the superficial portion of the skin that may join together to form larger lesions. Hives are closely related to angioedema. Hives, also called urticaria, are relatively common with at least 20% of the population having had at least one episode during their lifetime. Although seen in all ages, they seem to be more prevalent among young adults. The reaction involves the release of histamine from either mast cells or basophils causing an IgE (immediate type) mediated antibody response.

Itching is usually the first symptom. The wheals are white or red, occasionally with a pale center. Plaques are developed by 50% of patients and the lesions often come and go in different areas. In extreme cases, swelling in the throat may lead to a medical emergency.

The causes of urticaria are many and in 80% of cases never determined; not knowing the cause often results in an on-going problem. The most common causes of chronic urticaria are drug reactions, stress, food sensitivities and fungal infections. Some initiating factors include:

• Allergic urticaria: pollens, drugs, foods, animal dander, cosmetics, toxins from jellyfish or fleas
• Physical urticaria: heat or sun, cold, light, pressure from bracelets and clothes or scratching, vibration, exercise
• Secondary urticaria: infections (e.g. hepatitis B virus, candida albicans, streptococcal bacteria), collagen vascular diseases, cancer, psychological, hypothyroidism, polycythemia vera.

Lab findings are often unremarkable in cases of acute urticaria. For chronic urticaria, lab work should include CBC, ESR, UA, histamine levels and dental/sinus examinations to rule out hidden pathology.

Acute urticaria lasts from 1 to 7 days and treatment is not usually needed except to reduce the itching. The inciting agent must be dealt with, be it food, external agent or an emotion. In severe cases, epinephrine, as found in a bee sting kit, may be required.

In cases of chronic urticaria of over three weeks' duration, 50% of patients experience spontaneous remission within two years, even though in the majority of cases the cause is never identified.

Angioedema
While hives develop on the skin's surface, angioedema is a swelling of the deeper layers of the skin. It most often occurs on the hands, feet and face. In severe cases, normal breathing or swallowing can be blocked and emergency measures must be taken. This can occur if a person is extremely allergic to a specific food or drug.

Hives and angioedema may appear together or separately on the body. Angioedema usually lasts one or two days, and may reoccur with or without hives over an indefinite period of time.

Hereditary angioedema is a rare inherited disease which can be fatal in some cases and in this respect differs from other types of chronic angioedema. Swelling can occur in the airways, such as the larynx, tongue and throat, as well as on the face and other extremities. It has been demonstrated that a blood protein deficiency is the cause of this inherited illness.

Angioedema without a history of urticaria can be caused by certain drugs (ACE inhibitors), certain malignancies, and by an inherited enzyme deficiency (C1 esterase inhibitor deficiency). Symptoms of the hereditary enzyme deficiency problem typically include attacks of abdominal pain, vomiting, upper airway obstruction and visible non-itchy angioedema. This relatively rare disease requires treatment different from that of chronic urticaria and angioedema.