Nicotine liquids consist of nicotine diluted in either propylene glycol (PG) or vegetable glycerin (VG), both common food additives. PG e-juice (propylene glycol based) offers more flavor, lighter vapor than VG, but also a very slight possibility of allergic reaction. VG e-juice (vegetable glycerin based) produces a heavy vapor, but is not as flavorful as PG, and it tends to clog atomizers a little quicker than PG due to its thickness. They also have a variety of different flavorings added. Nicotine liquids sold separately for use in refillable cartridges are commonly referred to as "e-liquid" or "e-juice".

E-liquid is available in a variety of different flavors and nicotine concentrations. Nicotine concentrations range from high doses (to mimic the content of regular cigarettes) to midrange and low doses (that mimic the nicotine content of "light" and "ultralight" cigarettes). Liquids are also available which contain little or no nicotine.

Some flavors resemble traditional cigarette types, such as regular tobacco and menthol, and some even mimic specific cigarette brands, such as MLB Red or Kamal. e-liquids are also available with other flavorings, such as vanilla, chocolate, peach, strawberry, caramel, coffee, brandy, etc.

E-liquid strengths

• Super high strength: 36 mg of nicotine per ml of solution
  
• Extra high strength: 24 mg of nicotine per ml of solution
  
• High strength: 16 mg of nicotine per ml of solution
  
• Medium strength: 11 mg of nicotine per ml of solution
  
• Low strength: 6 mg of nicotine per ml of solution
  
• Non strength: 0 mg of nicotine per ml of solution
  

A small sample of e-liquid flavors