Wood’s Lamp Examination/ Ultraviolet Light Test

Last updated: February 8, 2026 Medically reviewed by: RxHarun Orthopedic Specialist Doctor Reading time: 2 min read

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.

Frequently Asked Questions

Is this article a replacement for a doctor?

No. It is educational content only. Patients should consult a qualified clinician for diagnosis and treatment.

When should I seek urgent care?

Seek urgent care for severe symptoms, rapidly worsening condition, breathing difficulty, severe pain, neurological changes, or any emergency warning sign.

References

Add references, clinical guidelines, textbooks, journal articles, or trusted medical sources here. You can edit this area later with a custom field named _rx_references.

Written by Dr. Harun Ar Rashid, MD - Arthritis, Bones, Joints Pain, Trauma, and Internal Medicine Specialist

Dr. Md. Harun Ar Rashid, MPH, MD, PhD, is a highly respected medical specialist celebrated for his exceptional clinical expertise and unwavering commitment to patient care. With advanced qualifications including MPH, MD, and PhD, he integrates cutting-edge research with a compassionate approach to medicine, ensuring that every patient receives personalized and effective treatment. His extensive training and hands-on experience enable him to diagnose complex conditions accurately and develop innovative treatment strategies tailored to individual needs. In addition to his clinical practice, Dr. Harun Ar Rashid is dedicated to medical education and research, writing and inventory creative thinking, innovative idea, critical care managementing make in his community to outreach, often participating in initiatives that promote health awareness and advance medical knowledge. His career is a testament to the high standards represented by his credentials, and he continues to contribute significantly to his field, driving improvements in both patient outcomes and healthcare practices. Born and educated in Bangladesh, Dr. Rashid earned his BPT from the University of Dhaka before pursuing postgraduate training internationally. He completed his MD in Internal Medicine at King’s College London, where he developed a special interest in inflammatory arthritis and metabolic bone disease. He then undertook a PhD in Orthopedic Science at the University of Oxford, conducting pioneering research on cytokine signaling pathways in rheumatoid arthritis. Following his doctoral studies, Dr. Rashid returned to clinical work with a fellowship in interventional pain management at the Rx University School of Medicine, refining his skills in image-guided joint injections and minimally invasive pain-relief techniques.