St. Luke's Hospital
Main Number: 314-434-1500 Emergency Dept: 314-205-6990 Patient Billing: 888-924-9200
Find a Physician Payment Options Locations & Directions
Follow us on: facebook twitter Mobile Email Page Email Page Print Page Print Page Increase Font Size Decrease Font Size Font Size
America's 50 Best Hospitals
Meet the Doctor
Spirit of Women
Community Health Needs Assessment
Home > Health Information

Multimedia Encyclopedia

    Print-Friendly
    Bookmarks

    Allergy testing - skin

    Patch tests - allergy; Scratch tests - allergy; Skin tests - allergy; RAST test

    Allergy skin tests aretests used tofind out which substances cause a person to have an allergic reaction.

    How the Test is Performed

    There are three common methods of allergy skin testing.

    The skin prick test involves:

    • Placing a small amount of substances that may be causing your symptoms on the skin, most often on the forearm, upper arm, or back.
    • Then, the skin is pricked so the allergen goes under the skin's surface.
    • The health care provider closely watches the skin for swelling and redness or other signs of a reaction. Results are usually seen within 15-20 minutes.
    • Several allergens can be tested at the same time.

    The intradermal skin test involves:

    • Injecting a small amount of allergen into the skin.
    • Then the health care provider watchesfor a reaction at the site.
    • This test is more likely to be used to find out if you are allergic to something specific, such as bee venom or penicillin.

    Patch testing is a method to diagnose the cause ofskin reactions that occur after the substance touches the skin.

    • Possible allergens are taped to the skin for 48 hours.
    • The health care provider will look at the area in 72 - 96 hours.

    How to Prepare for the Test

    Before any allergy testing, the health care provider will ask questions about:

    • Illnesses
    • Where you live andwork
    • Lifestyle
    • Foods and eating habits

    Allergy medicines can change the results of skin tests. Your doctor will tell you which medicines to avoid and when to stop taking them before the test.

    How the Test Will Feel

    Skin tests may cause very mild discomfort when the skin is pricked.

    You may have symptoms such as itching, a stuffy nose, red watery eyes, or a skin rash if you allergic to the substance in the test.

    Rarely, people can have a whole-body allergic reaction (called anaphylaxis), which can be life threatening. This usually only occurs with intradermal testing. Your health care provider will be prepared to treat this serious response.

    Why the Test is Performed

    Allergy tests are done to determinewhat substances are causing your allergy symptoms.

    Your doctor may order allergy skin tests if you have:

    • Hay fever (allergic rhinitis) and asthma symptoms that are notwell controlled with medicine
    • Hives and angioedema
    • Food allergies
    • Skin rashes (dermatitis), in which the skin becomes red, sore, orswollen after contact with the substance
    • Penicillin allergy*
    • Venom allergy

    *NOTE: Allergies to penicillin and closely related medicines are the only drug allergies that can be tested using skin tests. Skin tests for allergies to other drugs can be dangerous.

    The prick skin test may also be used to diagnose food allergies. Intradermal tests are not used to test for food allergies because of high false-positive results and the danger of causing a severe allergic reaction.

    Normal Results

    A negative test result means there were no skin changes in response to the allergen. This negative reaction most often means that you are not allergic to the substance.

    Rarely, a person may have a negative allergy test and still be allergic to the substance.

    What Abnormal Results Mean

    A positive result means you reacted to a substance. Your health care provider will see a red, raised area called a wheal.

    Often, a positive result means the symptoms you are having are due to exposure to that substance. In general, a stronger response means you are more sensitive to the substance.

    People can have a positive response to a substance with allergy skin testing, but not have any problems with that substance in everyday life.

    Skin tests areusually accurate. However, if the dose of allergen is large, even people who are not allergic will have a positive reaction.

    Your health care provider will consider your symptoms and the results of your skin test to suggest lifestyle changes you can make to avoid substances that may be causing your symptoms.

    References

    Bernstein IL, Li JT, Bernstein DI, Hamilton R, et al. American Academy of Allergy, Asthma and Immunology; American College of Allergy, Asthma and Immunology. Allergy diagnostic testing: an updated practice parameter. Ann Allergy Asthma Immunol. 2008 Mar;100(3 Suppl 3):S1-148.

    Demoly P, Bousquet J, Romano A. In vivo methods for the study of allergy. In: Adkinson NF Jr, ed. Middleton’s Allergy: Principles and Practice. 7th ed. Philadelphia, Pa: Mosby Elsevier; 2008:chap 71.

    Gober MD, DeCapite TJ, Gaspari AA. Contact dermatitis. In: Adkinson NF Jr, ed. Middleton’s Allergy: Principles and Practice. 7th ed. Philadelphia, Pa: Mosby Elsevier; 2008:chap 63.

    BACK TO TOP

    • Animation

    • Intradermal allergy test...

      illustration

    • Allergy skin prick or sc...

      illustration

    • Animation

    • Intradermal allergy test...

      illustration

    • Allergy skin prick or sc...

      illustration

    A Closer Look

    Self Care

    Tests for Allergy testing - skin

    Review Date: 6/17/2012

    Reviewed By: David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc., and Stuart I. Henochowicz, MD, FACP, Associate Clinical Professor of Medicine, Division of Allergy, Immunology, and Rheumatology, Georgetown University Medical School.

    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.
    adam.com

    A.D.A.M. content is best viewed in IE9 or above, Fire Fox and chrome browser.


    Back  |  Top
    About Us
    Contact Us
    History
    Mission
    Locations & Directions
    Quality Reports
    Annual Reports
    Honors & Awards
    Community Health Needs
    Assessment

    Newsroom
    Services
    Brain & Spine
    Cancer
    Heart
    Maternity
    Orthopedics
    Pulmonary
    Sleep Medicine
    Urgent Care
    Women's Services
    All Services
    Patients & Visitors
    Locations & Directions
    Find a Physician
    Tour St. Luke's
    Patient & Visitor Information
    Contact Us
    Payment Options
    Financial Assistance
    Send a Card
    Mammogram Appointments
    Health Tools
    My Personal Health
    mystlukes
    Spirit of Women
    Health Information & Tools
    Clinical Trials
    Health Risk Assessments
    Employer Programs -
    Passport to Wellness

    Classes & Events
    Classes & Events
    Spirit of Women
    Donate & Volunteer
    Giving Opportunities
    Volunteer
    Physicians & Employees
    For Physicians
    Remote Access
    Medical Residency Information
    Pharmacy Residency Information
    Physician CPOE Training
    Careers
    Careers
    St. Luke's Hospital - 232 South Woods Mill Road - Chesterfield, MO 63017 Main Number: 314-434-1500 Emergency Dept: 314-205-6990 Patient Billing: 888-924-9200
    Copyright © St. Luke's Hospital Website Terms and Conditions  |  Privacy Policy  |  Patient Notice of Privacy Policies PDF Sitemap St. Luke's Mobile