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    Drug allergies

    Allergic reaction - drug (medication); Drug hypersensitivity; Medication hypersensitivity

    Drug allergies are a group of symptoms caused by an allergic reaction to a drug (medication).

    Causes

    Adverse reactions to drugs are common. Almost any drug can cause an adverse reaction. Reactions range from irritating or mild side effects such as nausea and vomiting to life-threatening anaphylaxis.

    A true drug allergy is caused by a series of chemical steps in the body that produce the allergic reaction to a medication.

    The first time you take the medicine, you may have no problems. However, your body's immune system mayproduce a substance (antibody) called IgE against that drug. The next time you take the drug, the IgE tells your white blood cells to make a chemical called histamine, which causes your allergy symptoms. A drug allergy may also occur without your body producing IgE. Instead, it might produce other types of antibodies, or have other reactions that do not produce antibodies.

    Most drug allergies cause minor skin rashes and hives. Serum sickness is a delayed type of drug allergy that occurs a week or more afteryou are exposedto a medication or vaccine.

    Penicillin and related antibiotics are the most common cause of drug allergies. Other common allergy-causing drugs include:

    • Anticonvulsants
    • Insulin(especially animal sources of insulin)
    • Iodinated (containing iodine) x-ray contrast dyes (these can cause allergy-like reactions)
    • Sulfa drugs

    Most side effects of drugs are not due to an allergic reaction. For example, aspirin can cause nonallergic hives or trigger asthma. Some drug reactions are considered "idiosyncratic." This means the reaction is an unusual effect of the medication, not due to a predictable chemical effect of the drug. Many people confuse an uncomfortable, but not serious, side effect of a medicine (such as nausea) with a true drug allergy, which can be life threatening.

    Symptoms

    • Hives
    • Itching of the skin or eyes (common)
    • Skin rash (common)
    • Swelling of the lips, tongue, or face
    • Wheezing

    Symptoms of anaphylaxis include:

    • Abdominal pain or cramping
    • Confusion
    • Diarrhea
    • Difficulty breathing with wheeze or hoarse voice
    • Dizziness
    • Fainting, light-headedness
    • Hives over different parts of the body
    • Nausea, vomiting
    • Rapid pulse
    • Sensation of feeling the heart beat (palpitations)

    Exams and Tests

    An examination may show:

    • Decreased blood pressure
    • Hives
    • Rash
    • Swelling of the lips, face, or tongue (angioedema)
    • Wheezing

    Skin testing may help diagnose anallergy to penicillin-type medications. There are no good skin or blood tests to help diagnose other drug allergies.

    If you have had allergy-like symptoms after taking a medicine or receiving contrast (dye) before getting an x-ray, yourhealth care providerwill often tell you that this is proof of a drug allergy. You do not need more testing.

    Treatment

    The goal of treatment is to relieve symptoms and prevent a severe reaction.

    Treatment may include:

    • Antihistamines to relieve mild symptoms such as rash, hives, and itching
    • Bronchodilators such as albuterol to reduce asthma-like symptoms (moderate wheezing or cough)
    • Corticosteroids applied to the skin, given by mouth, or given through a vein (intravenously)
    • Epinephrine by injection to treat anaphylaxis

    The offending medication and similar drugs should be avoided. Make sure all your health care providers -- including dentists and hospitalstaff -- know about any drug allergies that you or your children have.

    Identifying jewelry or cards (such as Medic-Alert or others) may be recommended.

    Occasionally, a penicillin (or other drug) allergy responds to desensitization, where you are given larger and larger doses of a medicine to improve your tolerance of the drug. This should only be done by an allergist when there is no alternative drug for you to take.

    Outlook (Prognosis)

    Most drug allergies respond to treatment. However sometimes they can lead to severe asthma, anaphylaxis, or death.

    Possible Complications

    • Life-threatening, severe allergic reaction (anaphylaxis)
    • Asthma
    • Severe swellingunder the skin (angioedema), which can be life threatening if it affects the throat, tongue, or lungs
    • Death

    When to Contact a Medical Professional

    Call your health care provider if you are taking a medication and seem to be having a reaction to it.

    Go to the emergency room or call the local emergency number (such as 911) if you have difficulty breathing or develop other symptoms of severe asthma or anaphylaxis. These are emergency conditions.

    Prevention

    There is generally no way to prevent a drug allergy.

    If you have a known drug allergy, avoiding the medication is the best way to prevent an allergic reaction. You may also be told to avoid similar medicines. For example, if you are allergic to penicillin, you should also avoid amoxicillin or ampicillin.

    In some cases, ahealth care providermay approve the use of a drug that causes an allergy if you arefirst treatedwith corticosteroids (such as prednisone) and antihistamines (such as diphenhydramine). Do not try this without a health care provider's supervision. Pretreatment with corticosteroids and antihistamines has been shown to prevent anaphylaxis in peoplewho needto get x-ray contrast dye.

    Yourhealth care providermay also recommended "densensitization." This procedure must be done under close medical supervision. It involves giving very small doses of the medicine over a specific period of time. Do not try this without your health care provider's supervision.

    References

    Frew A. General principles of investigating and managing drug allergy. Br J Clin Pharmacol. 2011;71(5):642-646.

    Celik G, Pichler WJ, Adkinson NF Jr. Drug Allergy. In Adkinson NF Jr., ed. Middleton's Allergy: Principles and Practice. 7th ed. Philadelphia, Pa; Mosby Elsevier; 2008: chap 68.

    Grammer LC. Drug allergy. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 262.

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    • Anaphylaxis

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    • Hives

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    • Dermatitis, contact

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    • Drug rash, Tegretol

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    • Fixed drug eruption

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    • Drug rash on the back

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    • Antibodies

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      • Anaphylaxis

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      • Hives

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      • Allergic reactions to me...

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      • Dermatitis, contact

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      • Dermatitis, pustular con...

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      • Drug rash, Tegretol

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      • Fixed drug eruption

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      • Fixed drug eruption, bul...

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      • Drug rash on the back

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      • Antibodies

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      A Closer Look

        Talking to your MD

          Self Care

            Tests for Drug allergies

              Review Date: 5/6/2012

              Reviewed By: Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington; and Stuart I. Henochowicz, MD, FACP, Associate Clinical Professor of Medicine, Division of Allergy, Immunology, and Rheumatology, Georgetown University Medical School. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, 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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