Exodus 34:29-30

And it came to pass, when Moses came down from mount Sinai with the two tables of testimony in Moses' hand, when he came down from the mount, that Moses wist not that the skin of his face shone while he talked with him. And when Aaron and all the children of Israel saw Moses, behold, the skin of his face shone; and they were afraid to come nigh him.

This passage is generally believed to be the effects of being in the presence of God’s Glory which somehow lights up the the Human body, spirit or both.