Hives

This entry was posted by Sunday, 11 April, 2010
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Hives are 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-related nerve endings, causing the affected area to become itchy and sensitive.

A wide variety of substances may cause hives in sensitive people. Common culprits include:

  • Prescription and nonprescription drugs (Aspirin and penicillin are the two most commonly known causes of allergic reactions in adults.)
  • Nuts, especially peanuts, walnuts, and Brazil nuts
  • Fish, mollusks, and shellfish
  • Eggs
  • Wheat
  • Milk
  • Strawberries
  • Food additives and preservatives
  • Influenza vaccines
  • Tetanus toxoid vaccine
  • Gamma globulin
  • Bee, wasp, and hornet stings
  • Bites of mosquitoes, fleas, and scabies.

In addition, hives may also result from the body’s response to certain physical conditions, such as emotional stress, rubbing, cold wind, heat contact (prickly heat rash), wearing tight clothing, or exercise after a heavy meal.

Urticaria (hives) 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 others 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.
Hives are easily diagnosed by visual inspection. The cause of hives is usually apparent, but may require a careful medical history in some cases.

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.

Naturopaths or nutritionists will try to determine what allergic substance is causing the reaction and help the patient eliminate or minimize its effects. They may also recommend vitamin C, vitamin B12, and quercetin (a flavonoid) supplements to help control acute or chronic hives.

Mild cases of hives are treated with antihistamines, such as diphenhydramine (Benadryl). More severe cases may require such oral corticosteriods prednisone. Topical corticosteroids are not effective. In 2002, the Food and Drug Administration (FDA) approved the allergy drug Claritin for over-the-counter use for patients with urticaria. The drug comes in tablet and syrup form and carries little risk. Its release for over-the-counter use was delayed until the company that manufactures the drug could add instructions for patients about self-diagnosis of hives. They cautioned it should be used only for recurrent hives that had already been diagnosed by a physician, not for acute or severe urticaria. Airway swelling may require emergency injection of epinephrine (adrenaline).

Most cases of hives clear up within one to seven days without treatment, provided the cause (allergen) is found and avoided.
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.

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