Wood's lamp examination - Overview

Alternative Names

Black light test; Ultraviolet light test

Definition of Wood's lamp examination:

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

How the test is performed:

The test is done while you are seated in a dark room, usually in a dermatologist's office. The health care provider turns on the Wood's lamp, holds it 4 to 5 inches from the area of skin being studied, and looks for any skin color changes.

You should not 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 feel:

You will feel nothing during this test.

Why the test is performed:

Your health care provider may perform this test to detect several conditions affecting the skin, including

Bacterial infections
Fungal infections
Porphyria
Skin coloring changes

Wood's lamp test - of the scalp

Wood's lamp illumination

Reviewed last on: 10/8/2010
Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

References

Morelli JG. Evaluation of the patient. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 644.

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.

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