An inhaler was a medical device used by asthmatics.
Both Tom Osgood (COMIC: The Heralds of Destruction) and Petronella Osgood had an inhaler which they had to use when they became scared or excited. (TV: The Day of the Doctor, Death in Heaven) In 2020 Petronella found herself in need of a new prescription for her inhaler but was having trouble getting one as doctors were "all busy at the moment." (WC: The Zygon Isolation)
Petronella Osgood once used her inhaler as a weapon, against a version of herself from a parallel universe. (AUDIO: False Negative)