Breathing apparatus for medicating an airstream, compring a breathing apparatus (139), a medication chamber (138) adapted to store and discharge a therapeutic agent, a delivery pathway (141) between the chamber (138) and an intake air pathway and releasing means (145) for selectively discharging the therapeutic agent from the chamber (138) into the intake air pathway. The apparatus is particularly suited for scuba diving, snorkels, gas masks and filters. The invention is suitable for asthma sufferers but also extends to other respiratory diseases. Also claimed are a medication chamber for use in medicating an airstream and a method of medicating an airstream.