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Hives

Urticaria; Wheals

Hives are raised, often itchy, red bumps (welts) on the surface of the skin. They can be an allergic reaction to food or medicine. They can also appear without cause.

Causes

When you have an allergic reaction to a substance, your body releases histamine and other chemicals into the blood. This causes itching, swelling, and other symptoms. Hives are a common reaction. People with other allergies, such as hay fever, often get hives.

Angioedema is swelling of the deeper tissue that sometimes occurs with hives. Like hives, angioedema can occur on any part of the body. When it occurs around the mouth or throat, the symptoms can be severe, including airway blockage.

Many substances can trigger hives, including:

  • Animal dander (especially cats)
  • Insect bites
  • Medicines
  • Pollen
  • Shellfish, fish, nuts, eggs, milk, and other foods

Hives may also develop as a result of:

  • Emotional stress
  • Extreme cold or sun exposure
  • Excessive perspiration
  • Illness, including lupus, other autoimmune diseases, and leukemia
  • Infections such as mononucleosis
  • Exercise
  • Exposure to water

Often, the cause of hives is not known.

Symptoms

Symptoms of hives may include any of the following:

  • Itching.
  • Swelling of the surface of the skin into red- or skin-colored welts (called wheals) with clearly defined edges.
  • Wheals may get bigger, spread, and join together to form larger areas of flat, raised skin.
  • Wheals often change shape, disappear, and reappear within minutes or hours. It is unusual for a wheal to last more than 48 hours.
  • Dermatographism is a type of hives. It is caused by pressure on the skin and results in immediate hives.

Exams and Tests

Your health care provider can tell if you have hives by looking at your skin.

If you have a history of an allergy causing hives, for example, to strawberries, the diagnosis is even clearer.

Sometimes, a skin biopsy or blood tests are done to confirm that you had an allergic reaction, and to test for the substance that caused the allergic response. However, specific allergy testing is not useful in most cases of hives.

Treatment

Treatment may not be needed if the hives are mild. They may disappear on their own. To reduce itching and swelling:

  • Do not take hot baths or showers.
  • Do not wear tight-fitting clothing, which can irritate the area.
  • Your provider may suggest that you take an antihistamine such as diphenhydramine (Benadryl) or cetirizine (Zyrtec). Follow your provider's instructions or the package instructions about how to take the medicine.
  • Other oral prescription medicines may be needed, especially if the hives are chronic.

If your reaction is severe, especially if the swelling involves your throat, you may need an emergency shot of epinephrine (adrenaline) or steroids. Hives in the throat can block your airway, making it difficult to breathe.

Outlook (Prognosis)

Hives may be uncomfortable, but they are usually harmless and disappear on their own.

When the condition lasts longer than 6 weeks, it is called chronic hives. Usually no cause can be found. Most chronic hives resolve on their own in less than 1 year.

Possible Complications

Complications of hives may include:

  • Anaphylaxis (a life-threatening, whole-body allergic reaction that causes breathing difficulty)
  • Swelling in the throat can lead to life-threatening airway blockage

When to Contact a Medical Professional

Call 911 or your local emergency number if you have:

  • Fainting
  • Shortness of breath
  • Tightness in your throat
  • Tongue or face swelling
  • Wheezing

Call your provider if the hives are severe, uncomfortable, and do not respond to self-care measures.

Prevention

To help prevent hives avoid exposure to substances that give you allergic reactions.

References

Habif TP. Urticaria, angioedema, and pruritus. In: Habif TP, ed. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 6th ed. Philadelphia, PA: Elsevier; 2016:chap 6.

Saini SS. Urticaria and angioedema. In: Adkinson NF Jr, Bochner BS, Burks AW, et al, eds. Middleton's Allergy: Principles and Practice. 8th ed.  Philadelphia, PA: Elsevier Saunders; 2014:chap 36.

    • What are hives?

      What are hives?

      Animation

    •  

      What are hives? - Animation

      Learn the causes of hives, how to treat them, and when to call your doctor.

    • Hives (urticaria) - close-up

      Hives (urticaria) - close-up - illustration

      Hives develop when histamine is released into the small blood vessels (capillaries). The capillaries dilate which causes a welt, and fluid oozes into the surrounding tissue, causing swelling. Histamine also causes intense itching.

      Hives (urticaria) - close-up

      illustration

    • Food allergies

      Food allergies - illustration

      The body's immune system normally reacts to the presence of toxins, bacteria or viruses by producing a chemical reaction to fight these invaders. However, sometimes the immune system reacts to ordinarily benign substances such as food or pollen, to which it has become sensitive. This overreaction can cause symptoms from the mild (hives) to the severe (anaphylactic shock) upon subsequent exposure to the substance. An actual food allergy, as opposed to simple intolerance due to the lack of digesting enzymes, is indicated by the production of antibodies to the food allergen, and by the release of histamines and other chemicals into the blood.

      Food allergies

      illustration

    • Hives (urticaria) on the chest

      Hives (urticaria) on the chest - illustration

      Hives (urticaria) are raised, red, itchy welts, seen here on the chest. The majority of urticaria develop as a result of allergic reactions. Occasionally they may be associated with autoimmune diseases, infections (parasitosis), drugs, malignancy, or other causes.

      Hives (urticaria) on the chest

      illustration

    • Hives (urticaria) on the trunk

      Hives (urticaria) on the trunk - illustration

      This person has raised, red, itchy welts (urticaria) on the chest and abdomen. The majority of urticaria develop as a result of allergic reactions. Occasionally, they may be associated with autoimmune diseases, infections (parasitosis), drugs, malignancy, or other causes.

      Hives (urticaria) on the trunk

      illustration

    • Hives (urticaria) on the chest

      Hives (urticaria) on the chest - illustration

      The hives (urticaria) on this person's chest have the typical slightly-raised red appearance and are accompanied by itching. Hives can be generalized over the entire body or may be localized.

      Hives (urticaria) on the chest

      illustration

    • Hives (urticaria) on the back and buttocks

      Hives (urticaria) on the back and buttocks - illustration

      These are hives (urticaria) with the typical slightly-raised red appearance, and are accompanied by itching. These are located on the buttocks. Hives can be generalized over the entire body or may be localized, and usually result from an allergic reaction.

      Hives (urticaria) on the back and buttocks

      illustration

    • Hives (urticaria) on the back

      Hives (urticaria) on the back - illustration

      The hives (urticaria) on this person's back have the typical slightly-raised red appearance and are accompanied by itching. Hives can be generalized over the entire body, or may be localized.

      Hives (urticaria) on the back

      illustration

    • Hives

      Hives - illustration

      Hives are raised red welts of various size on the surface of the skin, often itchy, which come and go. Also called uticaria, hives is usually part of an allergic reaction to drugs or food. The term "dermatitis" describes an inflammatory response of the skin, caused by contact with allergens or irritants, exposure to sunlight, or by poor circulation, even stress. AVOID SCRATCHING. Scratching the rash may spread the inflammation, lead to infection and even leave scars.

      Hives

      illustration

    • Hives treatment

      Hives treatment - illustration

      When there is an allergic reaction in the body, a chemical called histamine, from specialized cells in the body tissues is released. Histamine causes allergy symptoms such as sneezing, itching, watery eyes, and runny nose. Antihistamines may reduce inflammation, itching, and swelling by blocking the effects of histamine, reducing the allergy symptoms.

      Hives treatment

      illustration

    • What are hives?

      Animation

    •  

      What are hives? - Animation

      Learn the causes of hives, how to treat them, and when to call your doctor.

    • Hives (urticaria) - close-up

      Hives (urticaria) - close-up - illustration

      Hives develop when histamine is released into the small blood vessels (capillaries). The capillaries dilate which causes a welt, and fluid oozes into the surrounding tissue, causing swelling. Histamine also causes intense itching.

      Hives (urticaria) - close-up

      illustration

    • Food allergies

      Food allergies - illustration

      The body's immune system normally reacts to the presence of toxins, bacteria or viruses by producing a chemical reaction to fight these invaders. However, sometimes the immune system reacts to ordinarily benign substances such as food or pollen, to which it has become sensitive. This overreaction can cause symptoms from the mild (hives) to the severe (anaphylactic shock) upon subsequent exposure to the substance. An actual food allergy, as opposed to simple intolerance due to the lack of digesting enzymes, is indicated by the production of antibodies to the food allergen, and by the release of histamines and other chemicals into the blood.

      Food allergies

      illustration

    • Hives (urticaria) on the chest

      Hives (urticaria) on the chest - illustration

      Hives (urticaria) are raised, red, itchy welts, seen here on the chest. The majority of urticaria develop as a result of allergic reactions. Occasionally they may be associated with autoimmune diseases, infections (parasitosis), drugs, malignancy, or other causes.

      Hives (urticaria) on the chest

      illustration

    • Hives (urticaria) on the trunk

      Hives (urticaria) on the trunk - illustration

      This person has raised, red, itchy welts (urticaria) on the chest and abdomen. The majority of urticaria develop as a result of allergic reactions. Occasionally, they may be associated with autoimmune diseases, infections (parasitosis), drugs, malignancy, or other causes.

      Hives (urticaria) on the trunk

      illustration

    • Hives (urticaria) on the chest

      Hives (urticaria) on the chest - illustration

      The hives (urticaria) on this person's chest have the typical slightly-raised red appearance and are accompanied by itching. Hives can be generalized over the entire body or may be localized.

      Hives (urticaria) on the chest

      illustration

    • Hives (urticaria) on the back and buttocks

      Hives (urticaria) on the back and buttocks - illustration

      These are hives (urticaria) with the typical slightly-raised red appearance, and are accompanied by itching. These are located on the buttocks. Hives can be generalized over the entire body or may be localized, and usually result from an allergic reaction.

      Hives (urticaria) on the back and buttocks

      illustration

    • Hives (urticaria) on the back

      Hives (urticaria) on the back - illustration

      The hives (urticaria) on this person's back have the typical slightly-raised red appearance and are accompanied by itching. Hives can be generalized over the entire body, or may be localized.

      Hives (urticaria) on the back

      illustration

    • Hives

      Hives - illustration

      Hives are raised red welts of various size on the surface of the skin, often itchy, which come and go. Also called uticaria, hives is usually part of an allergic reaction to drugs or food. The term "dermatitis" describes an inflammatory response of the skin, caused by contact with allergens or irritants, exposure to sunlight, or by poor circulation, even stress. AVOID SCRATCHING. Scratching the rash may spread the inflammation, lead to infection and even leave scars.

      Hives

      illustration

    • Hives treatment

      Hives treatment - illustration

      When there is an allergic reaction in the body, a chemical called histamine, from specialized cells in the body tissues is released. Histamine causes allergy symptoms such as sneezing, itching, watery eyes, and runny nose. Antihistamines may reduce inflammation, itching, and swelling by blocking the effects of histamine, reducing the allergy symptoms.

      Hives treatment

      illustration

    Review Date: 5/2/2017

    Reviewed By: David L. Swanson, MD, Vice Chair of Medical Dermatology, Associate Professor of Dermatology, Mayo Medical School, Scottsdale, AZ. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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