An inhaler comprising a reservoir of an inhalable composition. A housing contains the reservoir and has an outlet end and an opposite end. A composition flow path for the flow of the composition extends from the reservoir along the flow path and out of a composition outlet at the outlet end of the housing. A flexible diaphragm within the housing defines an air flow path from an air inlet to an air outlet at the outlet end of the housing, the diaphragm extending past the air flow inlet towards the opposite end separating the air flow path on one side of the diaphragm from the remainder of the housing on the opposite side of the diaphragm. A valve element is movable with the diaphragm and biased by a biasing force into a position in which it closes the composition flow path, wherein suction on the outlet end reduces the pressure in the air flow chamber thereby lifting the valve element against the biasing force to open the composition flow path； and wherein the biasing force is arranged to close the composition flow path once the suction ceases.
