It's green stuff that isn't very good for anyone drinking it, obviously, it's POISON for God's sake... If you don't cure it, you could die, since it makes you lose hitpoints. You could, on the other hand, also use it in your advantage, this can be done by dipping your weapons in it, though according to the logic of The Creators of Everything it is impossible to use poison with a sword or a scimitar.
And of course there is antipoison . It is the opposite of poison, therefore when it comes in contact with poison it explodes so violently that the explosion itself is teleported into another dimension and called a supernova. But everyone knows too much antipoison is bad for you, so if you drink more than one dose you'll die.