Nightfall, otherwise called nocturnal or nighttime emission, is a condition where a man expels semen involuntarily during sleep at night. It is a normal occurrence caused by the body’s need to eliminate extra sperm. This happens commonly during puberty but tends to improve with age. Eating less spicy food before going to bed, relaxing exercises, or wearing light clothes might help reduce such incidents. If this is disturbing you then feel free to talk with an adult whom you trust or seek help from a sexologist.