An inhaler (1) having, in an axial direction, a proximal end (P) for insertion into a user's mouth, and an opposite distal end (D) to the proximal end (P), in which the inhaler ( 1) comprises an inlet (4), an outlet (5) disposed at the proximal end (P), air passage (10, 11, 12, 13) extending from the inlet (4) to the outlet (5) , and a reservoir (8, 9) communicates with the air passage (10, 11, 12, 13) through a release hole (6, 7), the reservoir (8, 9) contains a dispersible substance, in wherein the inhaler (1) contains a proximal part (2) containing the outlet (5) and a distal part (3) attached to the proximal part (2) in which the proximal part (2) is linearly slidable along of the axial direction (A) with respect to the distal part (3) between an 'OPEN' position where the proximal part (2) is deployed from the distal part (3), and a 'CLOSED' position where the proximal part ( 2) retracts towards the distant part 1 (3), wherein the inhaler (1), further comprises an inlet valve member (14), and an outlet valve member (15)； - In which the tank (8,9) is arranged in the proximal part (2)； - In which the inlet (4) comprises one or more openings in a wall of the peripheral housing (20) of the proximal part (2), the one or more openings face radially outward, away from the axial direction ( A), and the inlet valve member (14) is formed by a wall of the peripheral housing (30) of the distal part (3) covering the openings the proximal part (2) when it is in the "CLOSED" position. - In which the outlet (5) comprises an axial orientation opening. - In which the outlet valve member (15) forms a plug attached to the distal part (3), the plug blocks the outlet (5) when the proximal part (2) is in the "CLOSED" position. - In which the release hole (6.7) is oriented in the axial direction (A)； and - wherein the inhaler (1) further comprises a reservoir valve member (16, 17), in which the reservoir valve member (16.17) forms a plug traveling in the axial direction (A) , the pin
