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Alternative namesBlack light test; Ultraviolet light test
DefinitionWood's lamp is a test that is performed in a dark room where ultraviolet light is shined on the area of interest.
How the test is performedYou will be seated and the lights will be turned off. After your eyes adjust to the darkness, your physician will turn on the Wood's lamp and hold it 4 to 5 inches from the area being studied. Your physician will then look at your skin for any color changes. (Take care not to look directly into the light.)
How to prepare for the test
No special preparation is needed. If you are treating the area in question with any topical medications, you may wish to skip an application before visiting the doctor.
How the test will feelYou will feel nothing during this test. Likewise, there should be no adverse side effects.
Why the test is performedYour health care provider may perform this test to detect several conditions, including:
Normal ValuesNormally your skin will not fluoresce, or shine, under the ultraviolet light.
What abnormal results mean
Using the light, your doctor may be able to confirm a diagnosis of fungal infection or bacterial infection. Your doctor may also be able to gain insight into the cause of light or dark colored spots on your skin.
What the risks areThere are no risks, but avoid looking directly into the ultraviolet light, as you avoid looking into the sun.
Do not wash before the test, because that may cause a false negative result. A room that is not dark enough may also alter results. Other materials may also glow. For example, some deodorants, make-ups, soaps, and even lint may be visible with the Wood's lamp.
Not all infections can be detected with the light. Some species of fungi and bacteria do not contain fluorescent chemicals.
Update Date: 4/15/2003Michael Lehrer, M.D., Department of Dermatology, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.
Last updated: Tue, 06 Jan 2009 00:20:03 GMT