• Knowledgebase: Information on Specific Illnesses

    Here you will find discussions of specific illnesses and their management.

    39. Hives (Urticaria) - Top

    Definition
    Raised red welts of various size on the surface of the skin, often itchy, associated with an allergic reaction and histamine release or abnormalities in the complement system or the kinin system (parts of the immune system).

    Causes, Incidence and Risk Factors
    About 1 out of 5 people experience urticaria (hives) at some time. Hives are more common in people who have experienced other allergic reactions, including hay fever and angioedema. The welts occur on the surface of the skin, usually in batches. Release of histamine and other chemicals into the bloodstream, associated with the allergic response, causes the itching, localized swelling, and other symptoms.
    Many substances, called allergens, can trigger an allergic response resulting in hives. Common allergens include:

    medications
    foods (such as berries, shellfish, fish, nuts, eggs, milk, and others)
    pollen
    animal dander (especially cats)
    insect bites
    exposure to water, sunlight, cold or heat
    emotional stress
    Hives may also develop after infections or illness (including autoimmune diseases, leukemia, and others). There seems to be a hereditary tendency toward the development of hives.
    Some nonallergic causes of hives include:

    dermographism
    cold urticaria
    lupus erythematosus (SLE)
    echinococcus infection (dog tapeworm)
    hereditary angioedema
    Henoch-Schonlein purpura
    mononucleosis
    hepatitis
    mastocytosis



    Symptoms
    itching (pruritus)
    swelling of the surface of the skin into red or skin colored welts (wheals) with clearly defined edges
    sudden onset
    rapid resolution
    welts blanch to touch
    new welts develop when the skin is scratched
    welts enlarge, spread or join together to form large flat raised areas
    welts change shape, disappear and reappear within minutes or hours
    Signs And Tests
    The diagnosis is primarily based on the appearance of the skin, and is confirmed by a history of exposure to an irritant or allergen. Occasionally, skin tests for allergy may be performed.


    Treatment
    Hives in the throat may obstruct the airway, so any swelling in the throat or difficulty breathing with hives are emergency symptoms. Treatment may not be needed if hives are mild, and they may disappear spontaneously.
    Antihistamines, adrenaline (epinephrine), terbutaline, cimetidine, corticosteroids, sedatives, or tranquilizers may reduce the inflammation, itching, and swelling.
    Self care:
    Cool compresses or soaks to the area may reduce swelling and pain. Avoid irritation of the area, and don't wear tight clothing (which may trigger a new outbreak). Avoid known allergens to prevent recurrence of hives.

    Expectations (Prognosis)
    Hives may be uncomfortable, but they generally are harmless and disappear on their own.

    Complications
    anaphylaxis
    life-threatening airway obstruction if swelling occurs in the throat
    - Updated: March 5, 2001

    [e-Mail me the Knowledgebase]-   [Search our Knowledgebase] -  [Question Not Answered?]    


    • James L Horwitz, MD

    David C. Thomas, MD

    Barbara Lindberg, PNP