For You -R

Dictionary of Philosophy and Psychology: By James Mark Baldwin (page 438)

Acute bodily diseases, fevers, fasting and exhaustion, dream-like states, certain forms of artificial hypnosis, and forms of heart trouble are also apt to induce hallucinations.

Looks like fasting is on the list. I think it depends on the person for how long someone would have to fast but it can cause hallucinations.

-L