Wood's Lamp: What It Shows During a Skin Examination

A Wood's Lamp is a filtered ultraviolet light used to highlight selected changes in skin colour and surface appearance.

A Wood's Lamp is a handheld or room-based device that shines filtered ultraviolet light on the skin in a darkened space. Some substances absorb or reflect this light differently from surrounding skin, creating a visible change in colour or brightness. The clinician uses that pattern as one part of a skin assessment, alongside the history and ordinary examination.

The area is usually clean and free of products that could glow under the lamp. You may be asked to close your eyes while the clinician examines the skin from a short distance. The light can help compare areas of altered pigmentation and may make certain surface clues from selected fungal or bacterial conditions more noticeable. The examination is brief and does not remove tissue.

A Wood's Lamp does not identify every rash, infection, or pigment disorder. Normal skin products, medicines, recent washing, and the natural colour of skin can affect what the clinician sees. A finding under the lamp is a clue rather than a complete diagnosis. Further examination, a skin scraping, or another test may be considered when the appearance remains uncertain.

Depending on the concern, a clinician may rely on direct examination, dermoscopy, a skin scraping, a swab, or a small sample of skin. These approaches answer different questions: a scraping can look for surface fungus, while a sample can help assess cells when a diagnosis cannot be made from appearance alone.

A brighter or different-looking area is interpreted together with its location, symptoms, duration, and appearance in normal light. A result may support a suspected diagnosis, make one explanation less likely, or show that another test is needed. It should not be read as a diagnosis in isolation.

The lamp is used for a short examination and should not be treated as a tanning device. Keep your eyes closed when directed and tell the clinician about products or medicines recently applied to the area. If the skin is very sensitive or irritated, the examination can be adapted or postponed.