Wood’s lamp examination is a tool healthcare providers use to examine your skin, scalp and hair. The lamp emits ultraviolet (UV) light, or blacklight, which makes certain types of cells glow or turn colors. This quick, painless test is often used to help diagnose fungal, bacterial and parasitic infections.
A Wood’s lamp examination is a simple test that can identify certain conditions on your skin, scalp and hair. It’s often used to help diagnose fungal, bacterial and parasitic infections.
The lamp uses long-wave ultraviolet (UV) light to make certain cells show color or appear fluorescent.
The tool, developed by American physicist Robert Wood, is also called:
Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy
Wood’s lamp examination can help healthcare providers diagnose several disorders, including:
Skin doctors called dermatologists often use Wood’s lamp. But other healthcare professionals also may perform the test, including primary care providers and nurses.
The tool also is used for nonmedical purposes. For example:
A Wood’s lamp emits black light, which is ultraviolet and can’t be seen by the naked human eye. It also emits a tiny bit of light on the violet spectrum, which can be seen by the naked human eye.
When the UV light shines on skin or another surface, some cells appear differently. Certain colors indicate healthy skin. Other colors, or a glowing appearance, might reveal unhealthy cells, such as fungus or bacteria.
Before a Wood’s lamp examination, your skin should be clean but not recently washed. Don’t apply makeup, deodorant, creams or other products to your skin or scalp before the test. Those products can affect the results.
A Wood’s lamp doesn’t emit any heat and the test is painless. Your healthcare provider will take the following steps to conduct a Wood’s light examination:
A UV light test is safe and doesn’t cause any skin damage. Very rarely, in people with extreme light sensitivity, the lamp can cause a temporary rash.
However, the lamp can cause damage to your eyes, particularly with repeat exposure. Your healthcare provider may ask you to close your eyes or wear protective goggles during the exam.
Your healthcare provider will discuss the results with you immediately after the test. To make a specific diagnosis, they also might consider your health history, symptoms and other test results.
Normal, healthy human skin under UV light looks bluish. Other colors on relatively healthy skin might be:
If your skin shows another color or glows (fluorescent or luminescent), it might reveal an infection or other condition. For example:
A note from Cleveland Clinic
Wood’s lamp examination is a simple, painless, risk-free test that can identify certain conditions on your skin, scalp and hair. The UV light test, along with your health history and symptoms, can help diagnose infections and other issues. The test takes only a few minutes and results are available immediately.
Last reviewed by a Cleveland Clinic medical professional on 06/17/2022.
Learn more about our editorial process.