Alternate Names: Black light test; Ultraviolet light test

How Performed: You 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:

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 It Feels: You will feel nothing during this test. Likewise, there should be no adverse side effects.

Risks: There are no risks, but avoid looking directly into the ultraviolet light, as you avoid looking into the sun.

Why Performed: Your health care provider may perform this test to detect several conditions, including:

• Bacterial infections
• Fungal infections
• Porphyria
• Pigmentary alterations

Normal Values: Normally your skin will not fluoresce, or shine, under the ultraviolet light.

Abnormal Results:

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.

Cost:

Special Considerations: Washing before the test 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.