An aerosol consists of solid or liquid particles suspended in a fine spray or mist. Aerosols used be a very popular way of applying just about everything from hair spray to shaving cream until it was found that the necessary propellants seem to be polluting the atmosphere. Aerosols tend also to be more expensive and sometimes less efficient than other, simpler forms of application. For example, an aerosol deodorant tends to squirt all over the room when you're trying to direct it towards your armpit whereas a roll-on is more controllable and less wasteful.
