Model human epidermal samples are used for transmission measurements at varying ambient humidity. Light is used
from four different light emitting diodes (LEDs), of UVA wavelength of 365nm, and three visible wavelengths of
460nm, 500nm, and 595nm. A humidity-controlled chamber was used to house the samples while transmission
measurements were taken. Many different types of measurements were taken, including raising ambient humidity from
20% to 75% then adding 0.5mL of water to the sample; lowering humidity from near 100% to 60%; and alternately
raising and lowering of the ambient humidity. The results show higher transmission of light through the samples at very
high ambient humidity, about 100%; whereas the transmission is much lower at lower ambient humidity. A simple
model of epidermis as a turbid medium and reduced light scattering by refractive index matching is used to explain the
results. Implications of these results are discussed.
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