Is nightfall harmful?

Sundowning.: Not usually. But it may be particularly difficult for one who sundowns.

Sexual health: "nightfall" is a term used in some cultures for nocturnal emissions -- ejaculating semen while the man sleeps. This is perfectly normal and is certain to happen to a man who does not have frequent ejaculations by himself or with a partner. Some people tell young men that it's dangerous -- this is superstition at best and is used to promote health frauds. Dad might be a great guy to talk to.