These are still quite new in Hong Kong, but in countries where they have been available for a while, they have been shown to have the potential to help smokers kick the habit.

According to a survey conducted by University College London, and published in the May 2014 issue of , smokers were 60 per cent more likely to report success in quitting smoking if they used e-cigarettes than if they used willpower alone or other nicotine replacement therapies, such as nicotine patches and chewing gum.

Electronic cigarettes are thought to have a number of benefits: they are smokeless and tobacco free, hence no carbon monoxide intake. They are also convenient to use as they require no matches, are battery operated, and can be used indoors in places that are smoke-free.

However, because e-cigarettes have been promoted as a safe alternative to conventional smoking, many e-cigarette users are unaware of their potential dangers. According to an article in the May issue of the , misinformation campaigns by e-cigarette manufacturers and investors are having an impact on the public's perception of safety, and evidence to support claims that e-cigarettes are safe is pending.

"Although e-cigarettes are conveniently smoke-less and tobacco free, they still contain nicotine and produce varying amounts of toxic and carcinogenic substances, such as propylene glycol," says Dr Winnie Mui, a general practitioner at Doctor Laura Bramley & Partners in Central.

"They also produce second-hand nicotine vapours, which contain carcinogenic formaldehyde. And the e-cigarette industry is largely unregulated, so there's a lack of full disclosure when it comes to the ingredients. Also, users can potentially become addicted to e-cigarettes."

A recent study by Greek cardiovascular specialist Dr Konstantinos Farsalinos found that e-cigarettes can cause lung damage and are not safer than regular tobacco cigarettes.

Then there is the issue of the potential dangers of e-cigarettes to children. Because e-cigarette vapour liquids are colourful and available in many tempting flavours such as cotton candy, cherry and chocolate, and the devices come in different shapes, sizes and colours, they may entice children, who may misuse them and harm themselves.

Liquid nicotine can be fatal in small amounts, Mui points out. A tablespoon of 10 per cent nicotine concentration liquid can kill an adult, while a teaspoon can kill a child. This liquid can be inhaled, ingested, or absorbed through the skin and eyes.

Before you make the switch, learn the short- and long-term effects of e-cigarettes.