An inhaler has an air inlet port and an entry passage extending from the air inlet port to a contact chamber inlet port, a contact chamber and an inhaler air outlet port. The contact chamber has first and second opposed ends, a sidewall extending between the first and second opposed ends that in cross section is curved, the second opposed end having an opening in air flow communication with a dosage chamber and a contact chamber outlet port. The contact chamber inlet port is provided in the sidewall and faces a portion of the sidewall opposed to contact chamber inlet port. The contact chamber has a cross sectional area that is greater than the cross sectional area of the entry passage.