Negates held items for five turns.

Magic Room disabled the effects of all held items for 5 turns.
Just as with the other 'Room' moves such as Trick Room, using Magic Room again while it is already active cancels the effect.
Magic Room also prevents:

• Using items through Natural Gift or Fing
• The Speed-boost gained from Macho Brace and other power items such as Power Weight.

Magic Room can not prevent:

• Using Mega Stones such as Gengarite to Mega Evolve
• Primal Reversion
  • A Kyogre using a Blue Orb
  • A Groudon using a Red Orb
• Any item that affects one of these categories:
  • prize money such as Amulet Coin
  • experience gain such as Lucky Egg
  • effort values such as Power Weight
  • friendship such as Soothe Bell
  • type of the target Pokémon
• Using berries through Bug Bite or Pluck
• Moving items from one Pokémon to another through Trick or Pickpocket.
• Poltergeist
• Teatime

If a Pokémon is already locked into a move through a choice item such as Choice Scarf and removes the item while affected by Magic Room, it will be affected by the Choice item lock bug.
The bug's specific behavior varies by generation but usually it locks the user into a move even when not holding a choice item.

• In Gen 5 Magic Room has a priority of -7 so it's used after every other move except Trick Room and Magic Room where the Speed of the user determines the order as usual.