Unburden doubles the Pokémon's Speed stat when the Pokémon's held item is used or lost. This includes items that were lost via Knock Off, Thief, Incinerate, Bug Bite, and Pluck, as well as if an Air Balloon popped. If there is no held item to begin with or if a held item is traded for another, Unburden will not be activated. This boost is lost if the Pokémon is switched out, loses Unburden, or gains a held item. Regaining Unburden if it had been lost does not restore a previous boost. If Unburden is suppressed with Neutralizing Gas, a new boost cannot be gained, but a previous boost will return once Neutralizing Gas leaves the field.
Gaining Unburden after a held item was consumed still doubles the Pokémon's Speed stat.
Outside of battle
Unburden has no effect outside of battle.