Not long ago, almost everyone washed their hands with plain old bar soap and water.

Times change.

Americans now spend almost $1 billion annually on soaps with antibacterial additives.

But do these products actually leave hands cleaner than soap and water would?

Maybe not, according to a study published recently in the Journal of Antimicrobial Chemotherapy.

The study investigated the effectiveness of soap containing triclosan [try-CLO-sann], one of the most popular antibacterial additives. Triclosan is prevalent in many antibacterial soaps, shampoos and other products.

In the study, researchers compared the germ-killing power of two soaps that were identical except that one contained 0.3 percent triclosan.

First, they tested the soaps on laboratory cultures of bacteria. Each culture received 20 seconds of exposure to one soap or the other. The results showed little difference in the number of bacteria killed.

The second experiment involved adult volunteers. Their hands were swabbed with cultured bacteria. The participants then used one of the soaps and washed vigorously for 30 seconds. Follow-up examination showed little difference between the soaps.

The researchers expected better performance from triclosan, and said one possible explanation for the outcome is that triclosan requires more exposure time for best results.

That may be true. But the volunteers washed for 30 seconds, the same amount of time many people wash their hands in real life.

Also, some studies in animals have shown that triclosan could disrupt hormone regulation. A 2010 University of Florida study found overexposure to triclosan might affect estrogen during pregnancy.

In any event, consumers should realize that soaps containing triclosan don’t trump bar soap for short washing sessions. If you expect otherwise, you might be wasting money.