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.

Demographics

Many children and adults experience hives at various times during their lives. As hives is not a reportable event, no accurate prevalence statistics are available.

Causes and symptoms

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

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 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.

When to call the doctor

A doctor or other healthcare professional should be called when hives do not spontaneously clear within a day of their appearance or when they include swelling of the throat. If the reactions are severe, as in anaphylactic reaction or shock, immediate medical care is needed.

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). More severe cases may require oral corticosteroids, such as prednisone. Topical corticosteroids are not effective. Airway swelling may require emergency injection of epinephrine (adrenaline).

An alternative practitioner will try to determine what allergic substance is causing the reaction and help the person 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.

Nutritional concerns

Hives may be triggered or worsened by caffeine or alcohol (in adults), or specific allergenic foods, which depend entirely on the patient. Avoiding these substances may reduce the occurrence of hives.

Parental concerns

Parents should monitor their children to ensure that any attack of hives does not involve the throat area. Young children should be encouraged not to stratch their skin too vigorously. If hives are a recurrent problem, parents should keep track of the foods the child eats in an attempt to discover the allergen.

KEY TERMS

Allergen —A foreign substance that provokes an immune reaction or allergic response in some sensitive people but not in most others.

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

Resources

BOOKS

Duvic, Madeleine. "Urticaria, Drug Hypersensitivity Rashes, Nodules and Tumors, and Atrophic Diseases." In Cecil Textbook of Medicine, 22nd ed. Edited by Lee Goldman et al. Philadelphia: Saunders, 2003, pp. 2475–85.

Frank, Michael M. "Urticaria and Angioedema." In Cecil Textbook of Medicine, 22nd ed. Edited by Lee Goldman et al. Philadelphia: Saunders, 2003, pp. 1610–3.

Leung, Donald Y. M. "Urticaria and Angioedema (Hives)." In Nelson Textbook of Pediatrics, 17th ed. Edited by Richard E. Behrman et al. Philadelphia: Saunders, 2003, pp. 778–80.

Yancy, Kim B., and Thomas J. Lawley. "Immunologically Mediated Skin Disorders." In Harrison's Principles of Internal Medicine, 15th ed. Edited by Eugene Braunwald et al. New York: McGraw-Hill, 2001, pp. 331–5.

PERIODICALS

Beltrani, V. S. "Urticaria: reassessed." Allergy and Asthma Proceedings 25, no. 3 (2004): 143–9.

Clarke, P. "Urticaria." Australian Family Physician 33, no. 7 (2004): 501–3.

Dice, J. P. "Physical urticaria." Immunology and Allergy Clinics of North America 24, no. 2 (2004): 225–46.

Grattan, C. E. "Autoimmune urticaria." Immunology and Allergy Clinics of North America 24, no. 2 (2004): 163–81.

Lawlor, F., and A. K. Black. "Delayed pressure urticaria." Immunology and Allergy Clinics of North America 24, no. 2 (2004): 247–58.

Rumbyrt, J. S., and A. L. Schocket. "Chronic urticaria and thyroid disease." Immunology and Allergy Clinics of North America 24, no. 2 (2004): 215–23.

Sheikh, J. "Advances in the treatment of chronic urticaria." Immunology and Allergy Clinics of North America 24, no. 2 (2004): 317–34.

ORGANIZATIONS

American Academy of Dermatology. 930 N. Meacham Road, PO Box 4014, Schaumburg, IL 60168–4014. Web site: <www.aad.org/>.

American Academy of Pediatrics. 141 Northwest Point Blvd., Elk Grove Village, IL 60007–1098. Web site: <www.aap.org/>.

WEB SITES

"Hives." MedlinePlus. Available online at <www.nlm.nih.gov/medlineplus/ency/article/000845.htm> (accessed January 6, 2005).

"Hives (Urticaria)." San Francisco State University Student Health Service. Available online at <www.sfsu.edu/~shs/skinclinic/urticaria.htm> (accessed January 6, 2005).

"Urticaria (Hives)." American Osteopathic College of Dermatology. Available online at <www.aocd.org/skin/dermatologic_diseases/urticaria.html> (accessed January 6, 2005).

L. Fleming Fallon, Jr., MD, DrPH

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.

hives (urticaria), rash consisting of blotches or localized swellings (wheals) of the skin, caused by an allergic reaction (see allergy ). The swelling is caused by distention of the skin capillaries and escape of serum and white cells into the skin and tissues. Hives are usually extremely itchy, and they may occur in a small area or cover virtually the entire body. The allergic reaction is commonly to a food or a drug, although injections of serum, insect bites, inhalants (pollen), and physical factors (cold, light, heat) may also be causative. Usually crops of hives come and go, remaining at one site for several hours and then reappearing at another; commonly an acute attack subsides spontaneously in a week or two. However, chronic cases of hives may last for long periods of time. Antihistamines and cortisone are considered helpful in relieving the itching and reducing the swelling.

Hives

What Are Hives?

Signs and Symptoms

What Is Angioedema?

Treatment for Hives

Can Hives Be Prevented?

Hives are itchy wheats (welts) that erupt on the skin, usually caused by an allergic reaction.

KEYWORD

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Allergy

What Are Hives?

Hives, also known as urticaria (ur-ti-KARE-e-a), develop as a reaction to various stimuli. Certain foods, food additives or dyes, drugs, alcohol, or viral infections can cause hives in susceptible people. Foods that commonly cause hives include milk, eggs, shellfish, strawberries, other fruits, and nuts.

Penicillin and aspirin cause hives in some people. Some viral infections that are known to cause hives are hepatitis (inflammation of the liver), infectious mononucleosis, and rubella (German measles).

Some people develop hives after vigorous exercise that causes them to sweat. Sometimes the sun or cold air can cause hives to appear on people’s skin. In some people, diving into cold water can result in severe hives—in a condition known as cold urticaria.

Signs and Symptoms

The first symptom of hives is itching, after which the wheals appear. Wheals usually are small, white welts with red, inflamed areas surrounding them; in some cases, however, they can be quite large. They usually erupt on the arms, legs, and trunk. Sometimes they develop into a ring, with the center clearing before the outer ring improves. Hives tend to come and go on different areas of the skin, and individual welts can last several hours.

What Is Angioedema?

A more severe form of hives, called angioedema (an-jee-o-e-DEE-ma), can cause swelling of the hands, feet, eyelids, lips, genital area, and airway passages, making breathing difficult. In some cases, angioedema is a hereditary disorder, and a family history usually is present. In these cases, it is a chronic condition, which means that it recurs from time to time.

Treatment for Hives

Most cases of hives clear up by themselves in 1 to 7 days. Some cases respond to medications such as antihistamines (an-tee-HISS-ta-meens) or corticosteroids (kor-ti-ko-STER-oids). Antihistamines are used to combat the allergic reaction, and corticosteroids are used to fight the inflammation.

Can Hives Be Prevented?

The only way to prevent hives is to avoid a known trigger (the substance that sets off the reaction). Many people who develop hives outgrow them over time without treatment.

See also

Allergies

Skin Conditions

hives (urticaria or nettle rash) Transient, itchy reddish or pale raised skin patches. Hives may be caused by an allergy, by irritants such as sunlight, or by stress.

hives / hīvz/ • pl. n. [treated as sing. or pl.] another term for urticaria.

hives (hyvz) n. see urticaria.