Providing hints can sometimes generate unexpected and even opposite results. A meta-analysis made at University of Michigan on 27 researches from 1980 to 2006 found that antibacterial soaps having triclosan as the main active chemical are no better at preventing infections than plain soaps.

In fact, these soaps could do more harm, as they can wipe the "good" bacteria of the skin, unbalancing the skin flora and decreasing the effectiveness of some common antibiotics, such as amoxicillin, due to the fact that commercial antibacterial soaps, unlike those employed in hospitals and clinics, have low concentrations of triclosan that do not kill bacterial species like Escherichia coli but in the same time allow them to develop resistance.

"What we are saying is that these E. coli could survive in the concentrations that we use in our (consumer-formulated) antibacterial soaps," said co-author Allison Aiello, of the U-M School of Public Health.

"What it means for consumers is that we need to be aware of what's in the products. The soaps containing triclosan used in the community settings are no more effective than plain soap at preventing infectious illness symptoms, as well as reducing bacteria on the hands," added Aiello.

A previous research at Tufts University's Alliance for the Prudent Use of Antibiotics found that overuse of triclosan could boost new strains of bacteria, thus "changing the kind of bacteria in our houses to those that may actually be harmful or resistant to antibiotics…" said Tufts' Dr. Stuart Levy.

Beyond Pesticides group has encountered an array of mutated bacterial strains resistant to triclosan and to some antibiotics. They also found that triclosan can be broken down when exposed to water and ultraviolet waves into dioxins, cancer inducing chemicals.

Dioxins are also known to weaken the immune system, lower fertility, change the levels of sex hormones and induce birth defects.

Are in this case alcohol-based soaps better? The issue is not clear. One research made at Colorado State University revealed that alcohol-based hand sanitizers were two times more effective at destroying germs on human hands than regular soaps.

But a Purdue University research found that this effect does not prevent more infections. Moreover, alcohol may kill the human body's own "good" bacteria by removing the skin's outer layer of oil.

It seems that in the end plain soap and warm water constitute by far the most effective method of fighting infections.