The Wood’s lamp examination is simply ultraviolet light used to show fluorescence, as in this photograph. The pink signifies the presence of bacteria causing erythrasma. A Wood’s lamp can show subtle skin pigment differences that would otherwise be very difficult to see in normal lighting. A Wood's lamp, as shown here, is used in a dark room and emits UVA light.
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Wood's Lamp Examination 

Picture of Wood's Lamp Examination: The Wood’s lamp examination is simply ultraviolet light used to show fluorescence, as in this photograph. The pink signifies the presence of bacteria causing erythrasma. Divider line
The Wood’s lamp examination is simply ultraviolet light used to show fluorescence, as in this photograph. The pink signifies the presence of bacteria causing erythrasma.
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Preparation / Typical Procedure
If it is known ahead of time that a Wood's lamp examination will be performed, it is best to not wash the area and not apply any cream to the skin to avoid inaccurate results. Most of the time, however, the decision to perform this test occurs at the time of the visit, in which case no preparation is necessary.

With the exam room lights turned off, the Wood's lamp is held by the physician approximately 5 inches from the area being examined. The UV light emitted by the lamp is shined directly on the patient's skin while the doctor looks for any colorful fluorescent changes that may suggest or confirm a particular diagnosis. This portion of the examination usually lasts less than a minute. Patients feel no discomfort from the exam.
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Last Modified: 22 Dec 2008
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