Hives Health Article

Definition

Hives is an allergic skin reaction causing localized redness, swelling, and itching.

Description

Hives is a reaction of the body's immune system that causes areas on the surface of the skin to swell, itch, and become reddened (wheals). These lesions are elevated, can be blanched with pressure applied from a finger, and are oval in shape. When the reaction is limited to small areas of the skin, it is called urticaria. Involvement of larger areas, such as whole sections of a limb, is called angioedema.

Causes

Hives is an allergic reaction. The body's immune system is normally responsible for protection from foreign invaders. When it becomes sensitized to normally harmless substances, the resulting reaction is called an allergy. An attack of hives is set off when such a substance, called an allergen, is ingested, inhaled, or otherwise contacted. It interacts with immune cells called mast cells, which reside in the skin, airways, and digestive system. When mast cells encounter an allergen, they release histamine and other chemicals, both locally and into the bloodstream. These chemicals cause blood vessels to become more porous, allowing fluid to accumulate in tissue and leading to the swollen and reddish appearance of hives. Some of the chemicals released sensitize pain-nerve endings, causing the affected area to become itchy (pruritic) and sensitive.

A wide variety of substances may cause hives in sensitive people, including food, drugs, insect or stings, and common household items. Common culprits include:

• nuts, especially peanuts, walnuts, and Brazil nuts
• fish, mollusks, and shellfish
• eggs
• wheat
• milk
• strawberries
• food additives and preservatives
• penicillin or other antibiotics
• flu vaccines
• tetanus toxoid vaccine

• gamma globulin
• bee, wasp, and hornet stings
• bites of mosquitoes, fleas, and scabies.
• dander from house pets
• new fragrances, laundry soaps, hand lotions, or articles of clothing
• certain plants, molds, chemicals, or dust particles

Symptoms

Urticaria is characterized by redness, swelling, and itching of small areas of the skin. These patches usually grow and recede in less than a day, but may recur in other locations, and complete resolution can take four to six weeks. Angioedema is characterized by more diffuse swelling. Swelling of the airways may cause wheezing and respiratory distress. In severe cases, airway obstruction may occur.

Diagnosis

Hives are easily diagnosed by visual inspection. The cause is usually more difficult to diagnose and requires a thorough medical history in order to determine the allergen.

Treatment

Mild cases of hives are treated with antihistamines, such as diphenhydramine (Benadryl). The major side effect of diphenhydramine is drowsiness. Newer antihistamines, such as loratadine (Claritin), are non sedating and are used more frequently with chronic hives management. More severe cases may require oral corticosteroids, such as prednisone. Prednisone helps block the release of mast cells and decreases the leakiness of blood vessel walls. Gradual tapering doses of prednisone are the most common way to take this medication. Topical corticosteroids are not effective. Airway swelling may require an emergency injection of epinephrine (adrenaline). Epinephrine constricts the blood vessels of the skin and immediately combats the histamine release.

An alternative practitioner will try to determine what allergic substance is causing the reaction and help the patient eliminate or minimize its effects. To deal with the symptoms of hives, an oatmeal bath may help to relieve itching. Chickweed (Stellaria media), applied as a poultice (crushed or chopped herbs applied directly to the skin) or added to bath water, may also help relieve itching. Several homeopathic remedies, including Urtica urens and Apis (Apis mellifica), may help relieve the itch, redness, or swelling associated with hives.

Prognosis

Most cases of hives clear up within one to seven days without treatment, providing the cause (allergen) is found and avoided. Some bouts of hives can persist up to six weeks and can be frustrating for the sufferer.

Health care team roles

The health care professional (R.N., L.P.N.) completing the history of a person presenting with hives should focus on specific information to determine the patient's allergen. Important information to include:

• Broad aspects about urticaria (when it started, how long and how often do episodes happen, where on the body do they usually appear, at what point do symptoms start to abate, and if there is a link with seasonal changes).
• Work and leisure activities (questions specific to possible exposure).
• Recent management of hives (previously prescribed medication, OTC medication or herbal supplements).
• Dietary review (a thorough review of the person's diet can help identify potential food substances that are common allergens).

KEY TERMS

Allergen—A substance capable of producing an immediate type of hypersensitivity or allergy.

Pruritic—Itchy.

Wheal—A smooth, slightly elevated area on the body surface, which is redder or paler than the surrounding skin.