If you think you don't have freckles, think again.

UV light shows New Yorkers their true skin

August 14, 2014: Photographer Thomas Leveritt set up an ultraviolet camera on a city street on a sunny day to show people how sunscreen helps protect your skin.

http://youtu.be/o9BqrSAHbTc

In the disturbing video shot in Brooklyn's Prospect Park, subjects see in real-time how much impact ultraviolet light has on them.

The footage shot by Thomas Leveritt shows how looks of joy turn to looks of shock and horror as the UV light shows previously invisible changes to their skin.

"I found that people reacted so strongly and interestingly to seeing themselves in UV, I decided I should capture that," Leveritt told Co.Create.

Almost everybody featured in the video is absolutely covered in hidden freckles, with the older participants more affected than the youths.

But the most remarkable part of the video is the impact that sunscreen has when applied.

Woods Lamp explained - used in skin analysis uses ultraviolet .

A Wood’s lamp is a mercury vapour ultraviolet lamp with a filter of barium silicate glass with 9% nickel oxide. The filter allows UV light in the wavelength of 320 to 400 nanometres only while blocking out all other wavelengths. Wood’s lamp mainly emits ultraviolet light in the wavelength of 360 nanometres.

Wood’s Lamp in the Diagnosis of Fungal Infection of the Scalp

Tinea capitis, the fungal infection of the scalp, is caused by different species of fungi. Examination of the scalp in a dark room with Wood’s lamp produces a greenish fluorescence when the infection is caused by certain species like the Microsporum and Trichophyton schoenleini. Wood’s lamp examination is particularly useful in rapidly diagnosing outbreak of tinea capitis in large number of cases as in community schools and boarding. Earlier diagnosis and management prevents further spread of the disease.

The disadvantage is that, at times, the fungal infection is caused by nonfluorescing species like Trihophyton violaceum. Hence a negative Wood’s lamp examination does not rule out presence of fungal infection.

Wood’s Lamp in Pigmentary Disorders of the Skin

In light-skinned individuals, it may be difficult to distinguish between normal skin and slightly hypo pigmented (light white colour) areas in diseases like pityriasis versicolor, pityriasis alba and ash leaf macules present in the genetic disease tuberous sclerosis. These are accentuated when examined under the Wood’s lamp. The extent of vitiligo patches also can be clearly delineated in the fair skinned with the help of the Wood’s lamp.

In pigmentary disorders like melasma and freckles, the level of melanin deposition can be differentiated using Wood’s lamp. Dark colour due to pigments in the outer epidermal layer of the skin is accentuated while the colour of the deeper dermal pigments is decreased during Wood’s lamp examination.

Wood’s Lamp Examination in the Diagnosis of Bacterial Infections of the Skin

Wood’s lamp fluoresce a coral pink colour in eythrasma, a superficial bacterial infection causing brownish red patches on the skin. A yellowish green fluorescence is typical of Pseudomonas pyocyanea infection.

Wood’s Lamp in the Diagnosis of Porphyrias

Porphyrias are a group of inherited and acquired disorders resulting from certain enzyme defects in the body. These could range from life threatening disease to disease limited to skin. In porphyrias, the urine is high-colored and the skin is highly photosensitive with other changes in hair, nails and other internal organs. A pinkish or orange red fluorescence of the urine accentuated by the addition of dilute hydrochloric acid helps in making a presumptive diagnosis of porphyiria cutanea tarda using Wood’s lamp. The same fluorescence is present in the stools and blister fluids of these patients.

Wood’s Lamp to Detect Scabies Burrows

Fluorescine or tetracycline rubbed into the skin allows the identification of scabies burrows under Wood’s light.

Similarly, drug deposits like tetracycline in the teeth and mepacrine in the nails can be diagnosed from the yellow fluorescence under Wood’s lamp examination.

Wood’s lamp, thus, is a simple and cost effective tool in the diagnosis of a variety of skin diseases.

Source:

Bedi BMS. Principles of Clinical Diagnosis in IADVL Textbook of Dermatology, 3rd Ed, 2008