An inhaler is a device which is used for delivering a particular amount of medicine to the lungs, which is taken in the form of little burst of aerosolized drugs. These drugs are inhaled by the patient. This delivery system is the most commonly used system to treat the patient of chronic obstructive pulmonary disease, asthma and other respiratory diseases.

Typical inhaler is constituted of three main components; an actuator (also called mouthpiece) which has the main function of directing the aerosol into the patient's lungs; the canister, which holds the formulation; and the metering valve, which allows a measured value of medication to be released with each actuation. The formulation is mainly constituted of the drug, a gas propellant which is in the liquefied form and, in majority of the cases, stabilizing excipients. The mouthpiece also contains the mating discharge nozzle and also has a dust cap to reduce the chances of contamination.

When one has to use the inhaler, he or she exerts a force on the top of canister, while supporting the lower end of the mouthpiece with their thumb. These inhalers are easy to operate and are the best and easily available option to control asthma.