City and county leaders all over Southern California are caught up in a frenzy of restricting the use of electronic cigarettes, with Los Angeles, Long Beach and San Bernardino officials taking steps this week to regulate them like tobacco products. A frenzy is just what this is, not reasoned deliberation.

The L.A. City Council voted unanimously Tuesday to impose new limits on where e-cigarettes can be sold, and said it would consider a proposal by Councilman Paul Koretz to limit their use in public places. City Attorney Mike Feuer said he believes e-cigarettes contain harmful chemicals. Disturbingly, Feuer added: “Until they are proven safe, we need to take action.”

That’s the backward thinking of promoters of the nanny state. A better policy, applicable to any such question, would be: Until they are shown to be unsafe, we need to pay attention but take no action.

L.A. Mayor Eric Garcetti should not sign the new rules into law. The Long Beach City Council should not act on the draft amendments it voted unanimously Tuesday to request from the city attorney. In San Bernardino County it may be too late to turn back, the board of supervisors having voted Tuesday to bar e-cigs from county-owned buildings, transit facilities and sports complexes, and within 20 feet of entrances; but officials should be ready to reverse course as facts dictate.

These are far from the first places in California and the United States to enact prohibitions against e-cigs, and we fear they won’t be the last.

Where’s momentum like this for legislative on issues of real, clear urgency?

Maybe ongoing study by public-health experts will provide convincing evidence that e-cigs are dangerous to those who enjoy them, or dangerous or particularly annoying to bystanders. Maybe it will be found that e-cigs’ use by kids is leading to a rise in real cigarette smoking. Maybe someone will debunk the claims that “vaping” is a healthier alternative to tobacco for many trying to quit.

Unless that happens, the regulators seem to be fueled mostly by fear of something new and trendy.

Shaped like cigarettes, battery-powered and filled with liquid nicotine and other flavorful additives that are converted into inhalable vapor, e-cigs were introduced in the U.S. a little over five years ago. Sales have soared from 50,000 in 2008 to 3.5 million in 2012 and are expected to top $1 billion this year. The national Centers for Disease Control earned headlines for the topic when it reported that 10 percent of middle- and high-school students used e-cigs in 2012, double the figure from the year before.

But in California, at least, state law already prohibits e-cigarette sales to minors. In many cities and counties, selling e-cigs requires a license. These steps should be the limit of the regulation unless more evidence of harm comes along.

Mimicking cigarettes does not make these devices the medical equivalent of cigarettes. They don’t produce smoke or tar. They don’t stink up a room.

The two kinds of cigarettes are not the same, and barring better evidence that e-cigarettes do harm, authorities’ actions this week are hasty.