The description is rather vague. Snakeblood reduces the negative effect of potion. But does it mean that when you put points in it, as a drinker it reduces the negative effect? Or, as a alchemist, you create a potion with less negative effect?
I am pretty sure it just for the alchemist with snake blood...
If you make a potion with negative effects and 1 positive one, and have 3 points in snake blood, you will recieve no negative effects from drinking the potion.
If you give that same potion away to someone who does not have snakeblood, they will indeed get the negative effects, as well as the positive ones.