Measurements of human bioluminescence.

In measuring the output of light from the human skin, we estimated the total photon rates to be of the order of 170-600 photons/s/cm2, depending on anatomical location. The light was strongest at the red end of the spectrum, but fell below detectable levels in the ultraviolet. Significant variations were observed between individuals in both photon rate and spectral profile. The photon rate also varied significantly with time for a single individual. The possible source of this light and its significance are discussed.