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    Wood's lamp examination

    Black light test; Ultraviolet light test

    A Wood's lamp examination is a test that uses ultraviolet (UV) light to look at the skin closely.

    How the Test is Performed

    You will sit in a dark room for this test.The testusually takes place ina dermatologist's office. The health care provider will turn on the Wood's lamp andhold it 4 - 5 inchesfrom the skin tolook for color changes.

    How to Prepare for the Test

    You do not need to take any special steps before this test.Ask your doctor if you avoid putting creams or medicineson the area of the skin being studies before the test.

    How the Test Will Feel

    You will feel nothing during this test.

    Why the Test is Performed

    Your health care provider maydo this to look for skin problems including:

    • Bacterial infections
    • Fungal infections
    • Porphyria
    • Skin coloring changes such as vitiligo

    Normal Results

    Normally your skin will not shine under the ultraviolet light.

    What Abnormal Results Mean

    A Wood's lamp exam may help your doctor confirm a fungal infection or bacterial infection. Your doctor may also be able to learn what is causing any light- or dark-colored spots on your skin.


    There are no risks. Avoid looking directly into the ultraviolet light.


    The following things can change the results of the test:

    • Washing your skin before the test (may cause a false-negative result)
    • A room that is not dark enough
    • Other materialsthatglow under the light, such as some deodorants, make-ups, soaps, andsometimes lint

    Not all types of bacteria and fungi show up underthe light.


    Harrison S, Piliang M, Bergfeld W. Hair disorders. In: Carey WD, ed. Cleveland Clinic: Current Clinical Medicine 2010. 2nd ed. Philadelphia, Pa: Saunders Elsevier; 2010.

    Morelli JG. Evaluation of the patient. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 637.


    • Wood's lamp test - of th...


    • Wood's lamp illumination


      • Wood's lamp test - of th...


      • Wood's lamp illumination


      A Closer Look

        Self Care

          Tests for Wood's lamp examination

          Review Date: 11/20/2012

          Reviewed By: Kevin Berman, MD, PhD, Atlanta Center for Dermatologic Disease, Atlanta, GA. Review provided by VeriMed Healthcare Network. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, Stephanie Slon, and Nissi Wang.

          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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          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
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