http://www.quantumbalancing.com/news/emitlight.htm
Mary Ann Liebert, Inc. - Error... 2006.12.31
Biophoton Emissions - Transcendental Meditation - Ultra Weak Photon Emission - UPE
Sorry for the external linking -- just a few articles about this topic. Photons are particles of light, as physicists call them. The photons emitted by human beings (and all living things) are said to be of an intensity range not percievable by the human eye, however there are already known exceptions to the general rulesets regarding what human beings can percieve. For example, it is widely known that those on the autism spectrum can percieve the refresh rate of flourescent lighting -- a rate of vision far too fast for most humans -- who typically have vision that runs around 60 Hz -- to see. Thus, it is now within the bounds of legitimate empirical observation that some may percieve auras / subtle bodies (as if thousands of years of written evidence in the far east weren"t enough).
Having studied physics, and all other *ahem* traits considered, I can"t say that this surprises me. For a particle of light to be emitted from anything, all that need happen is for an electron in any one of that thing"s molecules to be "demoted" -- that is, to lose energy and drop one quanta closer to the nucleus of its constituent atoms. Considering the constant and fluid exchange of energy between cells in all living things, it seems inconceivable that photons would not be both absorbed and released.
This also leads me to an observation regarding a physical reality of energy, and in regards to energy vampirism. Were any living being whatsoever to have a net energy state for their molecules that is below the normal threshold, then quanta of light would be absorbed. By the way, in physics, the smallest quanta of energy is called a photon as well, as particles of light are the universal currency of energy, at the most physically fundamental level.
Nice to see further scientific legitimacy added to an aspect of relatity we already know to be true