My question is are there actually photons within the body, especially the myelin sheath?
Yes - photons are released (or absorbed) by electrons, when electrons move up or down to a new energy level.
When the human body releases energy (creates heat), photons are released by electrons moving to a higher energy level.
The human body photons - "light" - are not in the visual range.
It is infrared light - heat - that is in a different spectrum than visible light.