Wood's light

Wood's light or Wood's lamp is a diagnostic tool used in dermatology to detect several conditions of the skin. The device emits ultraviolet (UV) light in the UVA range, around 365 nanometers, and is used in conjunction with the observation of skin under this specific light to diagnose and differentiate between various skin conditions.

History

Wood's light was invented in 1903 by American physicist Robert Williams Wood, using a filter that blocks visible light and allows UV light to pass through. This invention was a significant advancement in the field of dermatology, allowing for the non-invasive examination of skin conditions.

Usage

Wood's light examination is a simple, non-invasive procedure performed in a dark room. The light is shone onto the area of the skin in question, and the dermatologist observes the changes in color or fluorescence. This technique helps in diagnosing several conditions, including:

• Tinea capitis - a fungal infection that may fluoresce green under Wood's light.
• Erythrasma - caused by Corynebacterium minutissimum, shows coral-red fluorescence.
• Pseudomonas aeruginosa infections - which may emit a green fluorescence.
• Vitiligo - areas of skin lacking pigment appear bright white.
• Porphyria - a group of disorders that can show pink to red fluorescence in urine or teeth under Wood's light.

Limitations

While Wood's light can be a valuable diagnostic tool, it has limitations. Not all skin conditions will fluoresce under Wood's light, and the interpretation of results can be subjective. Additionally, the effectiveness of Wood's light can be influenced by external factors such as the presence of topical agents on the skin or the type of UV light source used.

Safety

Exposure to UV light can pose risks, including skin and eye damage. However, when used correctly and for short durations, Wood's light examinations are generally safe. Protective eyewear is recommended for both the patient and the practitioner during the examination.

Conclusion

Wood's light remains a useful diagnostic tool in dermatology, aiding in the diagnosis and differentiation of various skin conditions. Despite its limitations, when combined with other diagnostic methods, it provides valuable insights into the nature of skin disorders.

‎