Mist renders your Pokémon immune to most statistic-modifying attacks.
Attacks such as Leer and Growl will have no effect on a Pokémon that has
used Mist; nor will Accuracy-decreasing attacks like Flash. Attacks with statistic-modifying side
effects (such as Acid, which occasionally
lowers Defense) will do damage as normal, but will not produce their side
effect as long as Mist is in place.
Mist does not protect the user from confusion, status changes (eg, sleep or
poison), or Haze. It also does not protect the
user from statistic alterations associated with status changes, either in
the case of the Speed decrease caused by paralyzation, or the Attack
decrease caused by burns. Mist has no effect on any stat modifications
already in place at the time that it is used.
Mist does not prevent your Pokémon from boosting its own stats with
moves like Barrier or Growth.