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Research Letter
October 2016

The Role of Subtractive Color Mixing in the Perception of Blue Nevi and Veins—Beyond the Tyndall Effect

Author Affiliations
  • 1Division of Dermatology, University of California, Los Angeles, Los Angeles
  • 2Dermatology Service, Sacramento VA Medical Center, Mather, California
  • 3Keck School of Medicine, University of Southern California, Los Angeles
  • 4Department of Dermatology, University of California, Davis, Sacramento
  • 5Jules Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles
  • 6SUNY Downstate Medical Center Department of Dermatology, Brooklyn, New York
JAMA Dermatol. 2016;152(10):1167-1169. doi:10.1001/jamadermatol.2016.2201

The original study1 that proposed the “Tyndall effect” as the explanation behind the coloration of blue nevi drew from spectrophotometric data on cadaveric skin and not the direct study of blue nevi. Since then, the moniker of the Tyndall effect has been applied to a variety of blue phenomena in the skin despite a lack of confirmatory data. We hypothesized that other light-skin optical characteristics may provide a better explanation for the visual phenomenon associated with why blue nevi appear blue.

To briefly review the optics of the skin, perceived color is produced by light that strikes the skin and is remitted (a combination of light reflected and scattered back to the eye). The epidermis plays a minimal role in scattering, responsible primarily for the baseline reflectance of 5% to 7% of light from the skin surface.2 The Tyndall effect originally described the preferential scattering of shorter wavelength blue light through particulate matter in air and fluids, and its application to solid tissue optics is based on extrapolative hypotheses. Accordingly, such scattering would occur in a homogenous manner diffusely throughout the skin, not only in blue nevi, which led us to believe that the Tyndall effect does not fully account for the optics associated with blue nevi and veins.

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