Why do they occur? Doctors aren't one-hundred percent sure why wet dreams happen; however, they do have some theories. Some believe that nocturnal emissions occur because of an actual sexual dream and the process of becoming aroused by the dream. For instance, while a guy is asleep his body responds as if he was actually experiencing what he was dreaming of.
Another theory is that wet dreams are a way the body gets rid of "built-up" semen, and that "built-up" semen are due to a lack of masturbation. Yet, many doctors dispute this theory.
Testosterone-based drugs may be another factor in the occurrence of wet dreams. Studies have indicated that men who take testosterone-based drugs experience more wet dreams than the average male.
One last thing to note is that while asleep, "the body goes through a resting test of your sexual body parts," according to webmd.com. This means that males get erections about four to six times during an eight-hour period and females lubricate approximately the same amount of times.
