Here’s a neat little news article about humans glowing in the dark.
The human body literally glows, emitting a visible light in extremely small quantities at levels that rise and fall with the day, scientists now reveal.
Past research has shown that the body emits visible light, 1,000 times less intense than the levels to which our naked eyes are sensitive. In fact, virtually all living creatures emit very weak light, which is thought to be a byproduct of biochemical reactions involving free radicals.
We’re all glowing all the time throughout the entire spectrum as per Planck’s law. The radiation peaks very low in the infrared, by the time you’ve climbed up the spectrum there’s essentially no visible light emitted at human body temperatures. As such blackbody radiation isn’t what’s causing the observed glow here.
I don’t know enough about the science to say how likely the free radical hypothesis is, but on its face it’s not implausible. Chemical reactions tend to have roughly on the order of ~1 eV reaction energies, which is also generally around the visible part of the spectrum. It’s not at all implausible that a weak chemiluminescence could result.
Here’s the link to the actual photographs, which are sadly intensity plots and not true color. I’d be very interested in seeing a RGB composite.