Gordon Freeman is a smelly boy

It has occurred to me that throughout the entire series of Half-Life Gordon Freeman has never eaten, drunk, done his "washroom business", shaved, or even taken a bath for that matter. Let's not forget, with all that running he must work up a sweat. Also, in Left4Dead, how is it that 4 people can kill so many zombies but a whole city can't kill one? Plus, if get attacked by a zombie, you shoot the zombie, and the blood gets into your cut, don't you turn into a zombie?