There is a worrying lack of safety data on electronic cigarettes, despite their growing popularity with the public. 'E-cigarettes' look real, but are battery-powered and typically made of stainless steel. Users can inhale nicotine without tar, tobacco or carbon monoxide. Retailers argue e-cigarettes are a healthy alternative to the real thing but some studies have raised safety fears, says BBC News. The Department of Health is not aware of any evidence about the long-term safety of e-cigarettes and, as such, would suggest that consumers exercise caution. In the UK, it is illegal to sell e-cigarettes as a "quit smoking" aid.