To splash saliva to Macbook keyboard

It can definitely be harmful. Human saliva contains salt and salt is the enemy of electric devices. If it were get underneath the keys it could short things out.

There are plastic keyboard covers on the market too, like screen protectors.

Assuming it landed on a key top, just wipe it of gently and maybe try not to lean over your keyboard.

I suspect it is doing more harm to my trying to keep my lunch down than it is to your keyboard. ;-) I guess it depends upon how much. (No; I don't want to visualize that…) Try taking the edge of a tissue an don't press on it. Just let it absorb it.