"I think it's totally a marketing ploy to feed into people's fears about infection," said Neil Fishman, director of the antimicrobial management program at the University of Pennsylvania Medical Center.
There may be specific situations where the products can be helpful - such as places where water is not readily available. But for everyday use at home, "no one has shown that they do any good," said Stuart Levy, director of the Center for Adaptation Genetics and Drug Resistance at Tufts University. "Without a health benefit, the question is: Do we need them?"
SDA spokeswoman Janet Donohue said that the popularity of the products should speak to their benefits.
"Certainly their use for 30-odd years attest to the fact that they've been useful," she said.
The products do kill most bacteria that lurk on hands. And hands are one of the most common ways that infection is spread. Typically the bugs move from person to person, in a handshake, say. Or a person touching a doorknob or countertop can leave germs behind for someone else to pick up.
But soap, alcohol or peroxide do the job, too - by washing bacteria away.
What worries some scientists is that the flood of antibacterials may contribute to the growing problem of bacterial resistance to antibiotics. This resistance has made it harder for doctors to fight some potentially deadly germs.
Some of these products may eventually make us sicker by giving rise to bacteria that are resistant to them, said Levy, who has studied antibacterials. The more bacteria are exposed to them, he said, the more likely they are to develop ways of eluding them.
However, the Soap and Detergent Association and the Cosmetic, Toiletry and Fragrance Association said that Levy's conclusion was "misdirected," and that overuse of antibiotics was the real culprit of bacterial resistance. According to the Centers for Disease Control and Prevention, doctors in the United States write 50 million unnecessary prescriptions for antibiotics each year.
Though Levy agrees that antibiotic misuse is the principal problem, he said his research indicated that antibacterial products could also be a factor.
In his study, published last year in the journal Nature, Levy looked at how bacteria respond to triclosan, a common agent in antibacterial products. Triclosan kills bacteria by inhibiting their ability to reproduce.
Levy said his research showed that some bacteria were able to develop a "pumping method" to eject the chemical. Moreover, he said, because triclosan targets a particular part of the cell - a gene - it primes the bacteria for genetic mutations that may produce a hardier, more resistant strain.
In the lab, he said, bacteria that became resistant to triclosan also resisted antibiotics.
A study published last week in Nature, by Tennessee biologists, showed that E. coli bacteria with resistance to triclosan could withstand extremely high concentrations of the chemical.
There are good reasons why we wouldn't want to kill off bacteria unnecessarily. They live on every inch of the human being, from the skin, to the mouth, to the intestinal tract, and generally do no harm. They help digest food, make vitamins, and even ward off other bacteria.
Soap or antibacterials based on alcohol simply wash bacteria away, allowing the bacteria normally on hands to return.
But when people use antibacterials containing triclosan, they upset the natural balance, Levy said. Its residue can thwart the familiar bacteria, instead offering an opportunity for resistant bacteria to take their place.
"The healthy bacteria on our skin and in our intestinal tract are protecting us from the bacteria that aren't normally there," Levy said. "The bacteria that never were there before now have a chance to be there."
Last month, the American Medical Association urged the government to increase regulation of antibacterial products, concluding that there was no scientific data for "any proven infection-fighting benefit."
However, the AMA stopped short of discouraging use of the products. The FDA and FTC have also taken similar stances. Both have warned companies about falsely claiming that their antibacterial products can prevent illnesses. But neither agency went so far as pulling products off shelves.
The FTC, for instance, told Unilever, makers of Vaseline Intensive Care antibacterial lotion, to stop advertising that its product is "as effective or more effective than washing alone in protecting users against germs" or that it can reduce the risk of "developing colds, allergies, influenza, food-borne illnesses, or any other disease or disorder."
The company no longer uses such advertisements.
P. J. Brennan, an infectious-diseases specialist at the Hospital of the University of Pennsylvania, said certain situations - caring for the sick or working in food preparation - warrant using the products.
But in everyday life, he said, "it is unreasonable to expect that we can sterilize our environment. Bacteria are part of the normal ecology of our skin and water and all of our world."
Fishman agreed with his colleague, noting, "I don't use them at my house and I'm an infectious-disease doctor and my wife's an infectious-disease doctor."
The proliferation of antibacterials makes them hard to avoid at the drugstore or supermarket. Many people said they do not go out of their way to buy antibacterial products, but often end up with some because they are on sale.
Anita Ruby, who was with her children recently in Philadelphia's Rittenhouse Square, said she used antibacterial hand soap because her children tend to get in messes. But, she added, "I'm not sold on them. I use them because they're so out there. They're everywhere."
Kind of like the germs themselves.
Kelly Woo's e-mail address is email@example.com
WASHING YOUR HANDS Hand washing with simple soap and water is the single most effective tool to prevent the spread of infections caused by bacteria and viruses - everything from colds and flu to food poisoning and hepatitis. It even washes away lead dust.
The idea that hand washing could halt the spread of infection dates to the mid-1800s, when a young obstetrician in Vienna noticed that women whose babies were delivered by doctors or medical students were far more likely to acquire a deadly infection than women whose babies were delivered by midwives. The doctors, it turned out, went from dissecting cadavers to delivering babies - apparently transmitting disease from the corpses to the women in labor by way of their hands. Hand washing eventually took hold as an important mode of infection control in hospitals.
Who should wash?
Everyone should wash his or her hands. But attention to hand washing is particularly important where there are babies or people who are elderly or have chronic diseases. Both workers and children in day-care centers and nursery schools should wash frequently.
When should you wash?
Infectious-disease experts say a trip to the faucet is wise after coming in from school or work or even shopping; before eating; before and after preparing food; before touching a baby; and certainly after using the bathroom or changing a diaper.
How should you wash?
Just 15 seconds of vigorously rubbing your soaped-up hands back and forth under running water should do a decent job. Any basic soap will do because you are literally washing bacteria and viruses away. Hot water is best after handling raw chicken or beef because it helps to wash away greasy residues that might be contaminated.