Answer 1

A pokemon can hold an item such as Toxic/Burn Orb then switch it using a move such as Switcheroo (with Lopunny for example) so the opponent's pokemon is then holding it without your Pokemon being harmed by the item.

Comments

thanks trachy for buffing my answer up

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Just to add on: This means that you don't have to use Switcheroo right away (i.e: Opponent used Protect or Fake Out) You can try next turn and still not suffer a Burn or Poison