What should you know about a positive Wood's lamp test?

A Wood's lamp gives off ultraviolet light in a darkened room. Some skin pigments, scales, or microorganisms change the way light is reflected, so an area may appear brighter, lighter, or a different colour from nearby skin. The pattern and location matter more than the word positive alone. Cosmetics, creams, recently washed skin, and surrounding light can affect what the clinician sees.

The finding may support an assessment of conditions such as pigment loss or some superficial infections. Several unrelated conditions can produce similar fluorescence, while some affected skin does not fluoresce. The result needs to be considered alongside the history and a direct skin examination.

Ask which feature was seen, which diagnoses are being considered, and whether another examination or sample is needed. Follow the recommended treatment only after the clinician has matched the light pattern with your symptoms. Avoid applying new creams, bleaching products, or antiseptics to the area before review unless advised, because they can alter the appearance. Photographing a changing patch in consistent lighting can help track its borders, but it cannot replace an examination.

Arrange prompt medical review if the area is rapidly changing, painful, warm, draining, bleeding, or associated with fever. Seek urgent care for swelling around the eye, severe pain, confusion, or feeling faint. A positive light response alone is not an emergency; urgency depends on the skin changes and how you feel.

Ask: What did the light reveal? Could a cream or product have affected the result? Do I need a skin scraping, culture, biopsy, or follow-up examination? What changes should prompt an earlier review?