Fear expels water from the body. It can be expelled as sweat, as urine or as diarrhoea. Nervousness is also a form of fear, and thus may cause people to possibly go to the toilet more frequently than they may otherwise do (either to urinate or defecate, the latter which will be more fluid/less-viscous than normal for that person).
Epilepsy (related to rabies, which is also known as Hydrophobia) also causes people to expel water from their bodies, as well as contracting their throat muscles so that they cannot consume any fluids.
Nervous people are more likely to expel fluids, expelling fluids requires exocrine glands (be they large or small) so that water can leave the body. Males have fewer exocrine glands than females, but I don't know if the two are related in any way.