As the self-proclaimed authority on this matter, you have two options: Cognitohazard, for when it affects the subject, or Semiohazard, for when it affects the concept of lying itself.
The reasoning for the former has already been given by Meta (note that a cognitohazard is just the effect, not its means of transmission; it could still be toxicologic in case of an actual serum, memetic, psychotronic, you name it).
A semiohazard would rather affect the meaning of sign processes (Semiosis) in the vicinity. Such an effect would be much stronger, since somebody might just honestly believe a falsehood or have been fed missinformation. However, it is also much more dangerous, since you can pull shennenigans like a logical paradox or even better, something undecidable and probably screw with reality in the process.
However, having taken a peek at your sandbox, your Item has more of a compulsion effect, so "Cognitohazard" is broad enough.
