From wikipedia.. come on man these answers can be found in a matter of seconds on google.
Propylene glycol is used:
As a solvent in many pharmaceuticals, including oral, injectable and topical formulations. Notably, diazepam, which is insoluble in water, uses propylene glycol as its solvent in its clinical, injectable form.[5]
As a humectant food additive, labeled as E number E1520
As an emulsification agent in Angostura and orange bitters
As a moisturizer in medicines, cosmetics, food, toothpaste, shampoo, mouth wash, hair care and tobacco products
As a carrier in fragrance oils
As an ingredient in massage oils
In hand sanitizers, antibacterial lotions, and saline solutions
In smoke machines to make artificial smoke for use in firefighters' training and theatrical productions
In electronic cigarettes, as a vaporizable base for diluting the nicotine liquid
As a solvent for food colors and flavorings
As an ingredient, along with wax and gelatin, in the production of paintballs
As a moisture stabilizer (humectant) for snus (Swedish style snuff).
As a cooling agent for beer and wine glycol jacketed fermentation tanks
As a non-toxic antifreeze for winterizing drinking water systems, and in applications where the used antifreeze eventually will be drained into the soil, water, or a septic system.[6]
As a less-toxic antifreeze in solar water heating systems
As a solvent used in mixing photographic chemicals, such as film developers
In cryonics
As a working fluid in hydraulic presses
As a coolant in liquid cooling systems
To regulate humidity in a cigar humidor
As the killing and preserving agent in pitfall traps, usually used to capture ground beetles
As an additive to pipe tobacco to prevent dehydration.
To treat livestock ketosis
As the main ingredient in deodorant sticks.
To de-ice aircraft.[7]
As an ingredient in UV or blacklight tattoo ink
As a lubricant in air conditioning compressors.
As a wetting agent, used to determine drying time in paints and coatings
