A potion n-- Well, I hope you do not have it on you right now or the one I just gave you will be useless.

[ He scowls at Hijikata. Honestly! He's grudgingly grown to like the man, but sometimes he feels like he needs to hold their hand. Mortals really are just children playing at being adults. ]

Where did you get such a thing in the first place? Most enchanted items can only warn you of poisons; they do not render them harmless.