What is a Woods Lamp?

Woods Lamp - Cosmetic Composition.JPG

A creepy close-up pic of my freckled skin under a Wood’s Lamp

In the esthetics world, there are a variety of machines that we can use on clients to analyze and treat their skin. One very helpful tool to perform a skin analysis is the Woods Lamp which has some strong roots with science. A Wood’s lamp is a UV-emitting magnifying lamp that estheticians can use after cleansing to identify pigmentation and skin conditions of their client. The device was invented by Robert William Wood, an American Physicist, who figured how to put black filtered UV light into tubes for practical applications. The tool was soon picked up by dermatologists to use for recognition of fungal and bacterial infections of the skin and hair.

What is Fluorescence?

The main concept of a Wood’s Lamp is to illuminate conditions that are not visible to the naked eye. Wood’s lamps can illuminate fungi, bacteria, pigmentation and various other skin conditions (note: not skin types). But how is this even possible? A Wood’s Lamp must be used in complete darkness in order to allow the UV light to properly show what is visible at its wavelength. The Ultraviolet (UV) radiation wavelength stretches from 10nm – 400nm, with a Wood’s lamp sitting at around ~325nm. Despite traditionally only being able to see in the visible wavelength range, estheticians are able to see skin conditions due to fluorescence. Fluorescence “is the emission of light by a substance that has absorbed light or other electromagnetic radiation“. Certain biological substances have the ability to emit fluorescence – a very popular interdisciplinary research topic that involves chemistry, biology, and physics.

How does a Wood’s Lamp Show Skin Conditions?

Wood’s lamps allow estheticians and dermatologists to see pigmentation and skin conditions that are not visible traditionally. The use of a Wood’s lamp allows a visual of the conditions that lie in the dermis of the skin (the second and deeper skin layer). This is possible because of biofluorescence. Biofluroescence happens when pigmented skin cells (called fluorescent chromatophores) get their electrons excited – which can be triggered by the UV light and temporarily illuminate a fluorescence. During this electron excitement phase under the light, the viewer can see which colors appear on the skin’s surface. Fluorescence on the skin can appear in many ways which each color correlating to a pigment or skin condition.

White – thick corneum layer of dead skin cells

Blue/White – healthy skin (what the skin traditionally looks like under UV light)

Purple – dehydration

Yellow/Orange-ish – acne and/or acne bacteria (if the client does not suffer from acne, visiting a dermatologist could help characterize what bacteria is present)

Yellow/Pink/Orange-ish – Excess sebum or oil

Brown – hyperpigmentation, freckles or sun damage

Yellow/Green – hypopigmentation

So next time you’re able to treat yourself to a facial, try to stay awake through the skin analysis portion so you can talk to your esthetician about your glowing chromatophores!


I had so much fun researching and reading up for this post if you want to read more about this topic I’ve added links below to a few sites I found helpful. Yes, they’re mainly Wikipedia but they’re very extensive and well-written.








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