A Wood’s lamp test sometimes called the Blacklight test; the Ultraviolet light test, Wood’s lamp examination can be used to detect bacterial or fungal skin infections. It can also be used to detect skin pigment irregularities, like white patches on your skin called vitiligo, or corneal abrasions, which are scratches on your eye. It is sometimes used to select infected skin or hair for lab tests.
A Wood’s lamp examination is a procedure that uses transillumination (light) to detect bacterial or fungal skin infections. It also can detect skin pigment disorders such as vitiligo and other skin irregularities. This procedure can also be used to determine if you have a corneal abrasion (scratch) on the surface of your eye. This test is also known as the blacklight test or the ultraviolet light test.
Blacklight test; Ultraviolet light test, Wood’s lamp examination is a test that uses ultraviolet (UV) light to look at the skin closely.
How the Test is Performed
You sit in a dark room for this test. The test is usually done in a skin doctor’s (dermatologist) office. The doctor will turn on the Wood’s lamp and hold it 4 to 5 inches (10 to 12.5 centimeters) from the skin to look for color changes.
How to Prepare for the Test
You do not need to take any special steps before this test. Follow your doctor’s instructions about not putting creams or medicines on the area of the skin before the test.
How the Test will Feel
You will have no discomfort during this test.
Why the Test is Performed
This test is done to look for skin problems including:
- Bacterial infections
- Fungal infections
- Porphyria
- Skin coloring changes, such as vitiligo
Not all types of bacteria and fungi show up under the light.
Normal Results
Normally the skin will not shine under 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.
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 materials that glow under the light, such as some deodorants, make-ups, soaps, and sometimes lint
Risks
There are no risks with this test. DO NOT look directly into the ultraviolet light.
