E-cigarettes don’t make real smoke, yet they’ve ignited a firestorm of controversy.

You may have already seen e-cigarettes — electronic cigarettes — for sale on the Internet or at one of at least 62 kiosks at malls across the U.S.

What’s in them? The main component is a refillable or replaceable cartridge of liquid “juice” that contains nicotine, solvents, and flavors. When users draw on the device, it causes the battery to heat the liquid solution, which is then atomized into a vapor that can be inhaled. The claimed levels of nicotine vary. Blu e-cigs, for example, offer cartridges of different strengths, from no nicotine to approximately 13 to 16 milligrams, with each cartridge containing enough for 250 or more “puffs.”

E-cigarettes are marketed as a more socially permissible alternative to smoking. But what exactly are users — and the people around them — breathing in? Are the cigarettes safe? And with flavors such as Cherry Crush, Peach Schnapps, and Vivid Vanilla, to whom are they really marketed?

Are they safe to use? We don’t know yet. They expose users and people around them to fewer toxins than tobacco cigarettes, but that doesn’t mean they’re risk free. Nicotine is very addictive, so e-cigs — especially the fruit and candy-flavored ones — could hook young people on the stimulant, or serve as a gateway to real cigarettes, health officials warn.

And because they’re unregulated, you don’t necessarily know what’s in them. In 2009 the FDA detected diethylene glycol, a toxic chemical used in antifreeze, in some e-cig samples and carcinogens called nitrosamines in others. Questions also linger over secondhand “vapor.”

Do they help smokers quit? They might, though Consumer Reports points out that they’re not approved for that by the FDA. And, as with approved quitting methods, the results aren’t that impressive. In a study of 657 smokers published last fall, e-cigs were about as effective as nicotine patches and were slightly better than placebo e-cigarettes, which contain no nicotine.

Bottom line. The main reason it’s so hard to say whether e-cigarettes are safe is that they simply haven’t been around long enough to know. If you’re trying to give up real cigarettes, stick with better studied methods: nicotine gum, patches, and counseling. And if you don’t smoke, don’t start with e-cigs just for fun.