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    Hives

    Urticaria

    Hives are raised, often itchy, red bumps (welts) on the surface of the skin. They are usually an allergic reaction to food or medicine.

    Causes

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

    When swelling or welts occur around the face, especially the lips and eyes, it is called angioedema. Swelling can also occur around your hands, feet, and throat.

    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

    Symptoms

    • Itching
    • Swelling of the surface of the skin into red- or skin-colored welts (called wheals) with clearly defined edges.
    • Whealsmay get bigger, spread, and join together to form larger areas of flat, raised skin.
    • Whealscan also change shape, disappear, and reappear within minutes or hours.You know you have hives when you press the center of a wheal, it turns white. This is called blanching.

    Exams and Tests

    Your doctor can tell if you have hives by looking at your skin.

    If you have a history of an allergy, then the diagnosis is even more obvious.

    Sometimes,a skin biopsyor blood tests are done to confirm that you had an allergic reaction, and to test for the substance that caused the allergic response.

    Treatment

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

    • Do not takehot baths or showers.
    • Do not wear tight-fittingclothing, which can irritate the area.
    • Your health care provider may suggest that you take an antihistamine such as diphenhydramine (Benadryl).Follow your provider's instructions or package instructions about howto take the medicine.

    If your reaction is severe, especially if the swelling involves your throat, you may require an emergency shot of epinephrine (adrenaline) or a steroid. 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. In most cases, the exact cause of hives cannot be identified.

    Possible Complications

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

    Prevention

    • Avoid exposure to substances that give you allergic reactions.
    • Do not wear tight-fitting clothing anddo not takehot baths or showers just after having hives. These can cause hives to return.

    References

    Habif TP. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 5th ed. Philadelphia, Pa.: Elsevier Mosby; 2009:chap 9.

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    Self Care

      Tests for Hives

        Review Date: 5/15/2013

        Reviewed By: Kevin Berman, MD, PhD, Associate, Atlanta Center for Dermatologic Disease, Atlanta, GA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

        The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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