hives

Hives 

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 of the skin to swell, itch, and become reddened (wheals). 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 and symptoms

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 and sensitive.

A wide variety of substances may cause hives in sensitive people, including foods, drugs, and insect bites or stings. 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

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 be replaced by hives in other locations. 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 of hives is usually apparent, but may require a careful medical history in some cases.

Treatment

Mild cases of hives are treated with antihistamines, such as diphenhydramine (Benadryl) or desloratadine (Clarinex). Clarinex is non-sedating, meaning it will not make patients drowsy. More severe cases may require oral corticosteroids, such as prednisone. Topical corticosteroids are not effective. Airway swelling may require emergency injection of epinephrine (adrenaline).

Alternative treatment

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.

Prevention

Preventing hives depends on avoiding the allergen causing them. Analysis of new items in the diet or new drugs taken may reveal the likely source of the reaction. Chronic hives may be aggravated by stress, caffeine, alcohol, or tobacco; avoiding these may reduce the frequency of reactions.

Key terms

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

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

Resources

Periodicals

Kirn, F. Timothy. "Desloratadine Improves Urticaria in Clinical Setting." Skin & Allergy News September 2004: 41.

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hives (hīvz) urticaria.

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hives (hvz)

pl.n.

See urticaria.

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hives.

See urticaria.

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hives,

n See urticaria.

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hives

Urticaria, see there

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Patient discussion about hives.

Q. I was diagnosed with chronic urticaria. What is the reason for this condition? I was diagnosed with chronic urticaria last week after more than two months of urticaria (I have more than twenty 1 dollar coin area no my trunk that are red swollen and itchy). when I was younger I had a similar reaction too a bee sting and I was treated with an adrenalin shoot. Since that one time I never suffered from this kind of symptoms till two months ago. What can be the reason for this condition?

A. As was said before chronic urticaria is a symptom of many problems. I once took NSAIDs for knee pain and I started to itch myself. It took my doctor 3 weeks to understand that I was allergic to this specific drug. I also know that tomatoes can cause me an allergic reaction. Try to think is there anything new in your life? Tell it to the GP maybe he will be able to tell you if this is the reason for your symptoms.

Q. What can cause an angioedema on 15 year old girl? I’ve been getting angioedema signs on my left arm for the past few weeks, not severe but it itches and sure don’t help my low-as-it-is self esteem…

A. The following may cause angioedema -

Animal dander
Certain medications (drug allergy)
Emotional stress
Exposure to water, sunlight, cold or heat
Foods (such as berries, shellfish, nuts, eggs, milk, other)
Insect bites
Pollen

Hives or angioedema may also occur after an illness or infection.
Try to see if you were exposed to any of this and report it to your Dr.

Q. What caused my hives? I woke up this morning and saw that all my back and chest are covered in hives. How did this suddenly appear? What caused it?

A. Urticaria (hives) is generally an allergic reaction, or an immune response to food or some other allergen, but can also appear for other reasons, notably emotional stress.