Wood's lamp, also called Wood's light or LW, is a diagnostic device widely used in dermatology and aesthetics in order to verify the presence of skin lesions and their extension characteristics according to the fluorescence observed when the lesion analyzed is exposed to low wavelength UV light.
The analysis of the lesion in Wood's light should be done in a dark environment with no visible light so that the diagnosis is as correct as possible and, thus, the dermatologist can indicate the best treatment option.
What is it for
Wood's lamp is used to determine the degree and extent of the dermatological lesion, helping to diagnose and define treatment. Thus, LW can be used to:
- Differential diagnosis of infectious dermatoses, which can be caused by fungi or bacteria; Hypo or hyperchromic lesions, with vitiligo and melasma, for example; Porphyria, which is a disease characterized by the accumulation of substances in the body that are precursors of porphyrin, which can be detected in the urine, in addition to the evaluation of skin lesions; Presence of greasiness or dryness of the skin, and LW can be used before cosmetic procedures, as it allows the professional to check the characteristics of the skin and determine the most appropriate aesthetic procedure for that type of skin.
According to the luminescence color, it is possible to identify and differentiate dermatological lesions. In the case of infectious dermatoses, fluorescence represents the infectious agent, but in the case of porphyria, fluorescence occurs depending on the substances present in the urine.
In the case of pigmentation disorders, the Wood lamp is used not only to assess the limits and characteristics of the lesion, but also to check for the presence of subclinical lesions that were not identified in conventional dermatological examination, just by fluorescence.
Although the use of the Wood lamp is very effective in diagnosing and monitoring the evolution of lesions, its use does not dispense with conventional dermatological examination. Understand how the dermatological exam is done.
How it works
Wood's lamp is a small and inexpensive device that allows the identification of several dermatological lesions according to the fluorescence pattern observed when the lesion is illuminated at a low wavelength. UV light is emitted at a wavelength of 340 to 450 nm by an arc of mercury and is filtered through a glass plate composed of barium silicate and 9% nickel oxide.
For the diagnosis to be the most correct, it is necessary that the evaluation of the lesion by the Wood's lamp is made 15 cm from the lesion, in a dark environment and without visible light, so that only the fluorescence of the lesion is perceived. The fluorescence pattern of the most frequent dermatological lesions are:
| Disease | Fluorescence |
| Dermatophytoses | Blue-green or light blue, depending on the species causing the disease; |
| Pityriasis versicolor | Silvery yellow |
| Erythrasma | Orange-red |
| Acne | Green or reddish-orange |
| Vitiligo | Bright blue |
| Melasma | Dark brown |
| Tuberous sclerosis | White |
| Porphyria | Red-orange urine |
