An aerosol is defined as a suspension of liquid or solid particles in air or oxygen; the process of forming an aerosol is called nebulization. The purpose of aerosol treatment is to deposit these particles on the respiratory epithelium where a high local concentration can be achieved and exert its pharmacological effect. Hopefully, only a small amount of the particles will be absorbed, and thus, significant systemic and allergic effects will be avoided.
In all likelihood, crude aerosol preparations have been used for medical purposes since antiquity. As early as the 12th century, a scientific treatise described the use of a simple aerosol (steam) in the treatment of asthma.1 In recent years, with the development of more sophisticated techniques and equipment, aerosol therapy has greatly expanded in use. Even today, however, the problems involved in producing a stable particle of uniformly correct size, which will be nonhygroscopic and nonabsorbable
Harris RL, Riley HD. Reactions to Aerosol Medication in Infants and Children. JAMA. 1967;201(12):953–955. doi:10.1001/jama.1967.03130120061015