The Wood’s Lamp: The Classic Tool for Pigment Depth
The Principle
A Wood’s lamp emits 365 nm long-wave UV: chromophores fluoresce — epidermal melanin absorbs UV strongly and darkens (a shadow), dermal pigment gets masked by collagen scattering and fades, while sebum and porphyrins glow orange-red. It is the cheapest tool for pigment depth typing.
Use in Pigment Work
| Under the lamp | Means | Treatment meaning |
|---|---|---|
| Sharper, darker borders | Epidermal pigment (freckles, lentigines) | High clearance efficiency (freckles) |
| Fading or vanishing spots | Dermal pigment (nevus of Ota, some melasma) | Long wavelengths, more sessions (the melasma strategy) |
| Mixed | Mixed type (common in long-standing melasma) | Layered combination plans |
| Orange-red dots | C. acnes porphyrins, sebum | Oily/acne management reference (acne) |
Operation Points
- Dark room: full darkness works best (curtains + lights off).
- Distance: 10-15 cm; never shine into eyes (client’s eyes closed, operator avoids direct view).
- Compare: read against normal light; record the differences.
- Archive: lamp photos filed separately labeled from standard shots.
Limits and Boundaries
- Low contrast on deeply pigmented skin — experience demanded.
- Lamp aging changes brightness — calibrate periodically.
- It is a typing adjunct: complex cases like melasma still rest on clinical synthesis.
FAQ
Does it reveal “hidden spots”?
Yes — epidermal pigment not yet visible in normal light (early lentigines), which is its consultation-showcase value: “see your future under the lamp” lands strongly.
Buy a home Wood’s lamp?
Untrained self-reading adds little; it’s a professional tool with far more clinic value than home value.