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


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


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 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.


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


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.


Most cases of hives clear up within one to seven days without treatment, providing 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.

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.



Kirn, F. Timothy. "Desloratadine Improves Urticaria in Clinical Setting." Skin & Allergy News September 2004: 41.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


a vascular reaction of the skin marked by transient appearance of slightly elevated patches (wheals) that are redder or paler than the surrounding skin and often attended by severe itching; the cause may be certain foods, infection, or emotional stress. (See Atlas 2, Plate D.) Called also hives. adj., adj urtica´rial.
cold urticaria urticaria precipitated by cold air, water, or objects, occurring in two forms: In the autosomal dominant form, which is associated with fever, arthralgias, and leukocytosis, the lesions occur as erythematous, burning papules and macules. The more common acquired form is usually idiopathic and self-limited.
giant urticaria angioedema.
urticaria hemorrha´gica purpura with urticaria.
urticaria medicamento´sa that due to use of a drug.
papular urticaria (urticaria papulo´sa) an allergic reaction to the bite of various insects, with appearance of lesions that evolve into inflammatory, increasingly hard, red or brownish, persistent papules.
urticaria pigmento´sa the most common form of mastocytosis, occurring primarily in children, manifested as persistent pink to brown macules or soft plaques of various size; pruritus and urtication occur on stroking the lesions.
urticaria pigmentosa, juvenile urticaria pigmentosa present at birth or in the first few weeks of life, usually disappearing before puberty, taking the form of a single nodule or tumor or of a disseminated eruption of yellowish brown to yellowish red macules, plaques, or bullae.
solar urticaria a rare form produced by exposure to sunlight.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


An eruption of itching wheals, collquially called hives, usually of systemic origin; it may be due to a state of hypersensitivity to foods or drugs, foci of infection, physical agents (heat, cold, light, friction), or psychic stimuli.
Synonym(s): hives (1) , urtication (2)
[L. urtica]
Farlex Partner Medical Dictionary © Farlex 2012


pl.n. (used with a sing. or pl. verb)
A rash characterized by intensely itching welts, triggered by the release of histamine and caused by an allergic response to any of multiple agents or conditions, including food, drugs, and infections. Also called nettle rash, urticaria.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


A condition characterised by pruritic, raised red welts on the skin (dermographism), associated with allergic reactions and histamine release or defects in the complement or kinin systems.
Risk factors
Prior allergic reactions—e.g., hay fever and angioedema.

Urticaria triggers
- Animal dander (especially cats)
- Drugs/medication
- Emotional stress
- Food (e.g., berries, shellfish, fish, nuts, eggs, milk)
- Immune—hereditary angiooedema
- Infection—echinococcus infection (dog tapeworm)
- Inflammation (e.g., mononucleosis, hepatitis)
- Insect bites
- Mastocytosis
- Mechanical stimulants (e.g., water, sunlight, cold or heat)
- Pollen
- Post-infection
- Other disease
   • Autoimmune diseases, systemic lupus erythematosus
   • Henoch-Schönlein purpura
   • Leukaemia, etc.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.


Urticaria, see there.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.


An eruption of itching wheals, usually of systemic origin; it may be due to a state of hypersensitivity to foods or drugs, foci of infection, physical agents (e.g., exercise, heat, cold, light, friction), or psychic stimuli.
Synonym(s): hives (1) , urtication (3) .
[L. urtica]


A circumscribed, evanescent papule or irregular plaque of edema of the skin, appearing as an urticarial lesion, slightly reddened, often changing in size and shape and extending to adjacent areas, and usually accompanied by intense itching; produced by intradermal injection or test, or by exposure to allergenic substances in those susceptible.
Synonym(s): hives (2) , welt.
[A.S. hwēle]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005


An eruption of itching wheals, colloquially called hives, usually of systemic origin; may be due to a state of hypersensitivity to foods or drugs, foci of infection, physical agents (heat, cold, light, friction), or psychic stimuli.
[L. urtica]


Circumscribed, evanescent papule or irregular plaque or dermal edema, appearing as an urticarial lesion, slightly reddened, often changing in size and shape and extending to adjacent areas, and usually accompanied by intense itching; produced by intradermal injection or test, or by exposure to allergenic substances in susceptible people.
[A.S. hwēle]
Medical Dictionary for the Dental Professions © Farlex 2012

Patient discussion about hives

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.

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. hpv Can i get pregnant

A. You can get pregnant you just need to tell your doctor whats going on so he can keep an eye on the issue.

More discussions about hives
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