Doing It Wrong: Hot Water and Antibacterial Soap Don't Help Kill Germs

By Wesley Fenlon

Cold water works just as well as hot water, says a Vanderbilt study. Plain old soap is just as effective as antibacterial, says the FDA.

We all thought we knew how to wash our hands. We're taught the basics as young kids: Use hot water to help kill germs and bacteria. Use antibacterial soap to get your hands squeaky clean. And now it turns out that neither of those bits of advice are actually true. The world has just been turned upside-down, and its hands are dirty.

First, that business about hot water. It's true that hot water will kill off bacteria, but only at temperatures that would seriously damage your skin. National Geographic, reporting on a Vanderbilt University study, writes "boiling water, 212°F (99.98°C), is sometimes used to kill germs-for example, to disinfect drinking water that might be contaminated with pathogens. But 'hot' water for hand washing is generally within 104°F to 131°F (40°C to 55°C.) At the high end of that range, heat could kill some pathogens, but the sustained contact that would be required would scald the skin."

Cold water, is just as effective at washing hands as lukewarm or hot water. 40°F (4.4°C) cold water appeared to be just as effective as hot in Vanderbilt's study, carried out by research assistant professor Amanda Carrico. Carrico even points out that heating water to wash hands is incredibly wasteful.

Photo credit: Flickr user skypream via Creative Commons

Americans collectively wash their hands 800 billion times per year, and about 64 percent of the time it's using wastefully warm water. The waste adds up to create a few depressing numbers--six million tons of unnecessary CO2 emissions, aka two coal power plants or the entirety of Barbados' annual emissions. We should probably stop washing our hands with hot water.

Now, the soap thing: AP reports that the results of some 40-year studies are in, and the government finally agrees that antibacterial soaps aren't doing much good. "After more than 40 years of study, the U.S. government says it has found no evidence that common anti-bacterial soaps prevent the spread of germs, and regulators want the makers of Dawn, Dial and other household staples to prove that their products do not pose health risks to consumers," writes the Associated Press.

At the beginning of 2013, we wrote about studies concerning the antibacterial agent Triclosan. The antibacterial agent isn't just in soap, but in everyday household objects like pizza cutters. Scientists were worried that its overuse was creating resistant bacteria, and studies also showed it posing health risks to some people, aggravating symptoms of asthma and allergies.

Those studies just got backup. The AP writes: "Scientists at the Food and Drug Administration announced Monday that they are revisiting the safety of triclosan and other sanitizing agents found in soap in countless kitchens and bathrooms. Recent studies suggest triclosan and similar substances can interfere with hormone levels in lab animals and spur the growth of drug-resistant bacteria. The government's preliminary ruling lends new support to outside researchers who have long argued that the chemicals are, at best, ineffective and at worst, a threat to public health."

Plain old soap may be just as effective, and ultimately better for you, than the antibacterial variety. And hand sanitizers that use alcohol also avoid the potential pitfalls of antibacterial agents while still being effective.

For their part, the antibacterial soap makers say they have sent the FDA data proving antibacterial soap is more effective at killing germs. Even if they're right, we should probably cut back on the use of triclosan in the objects we use to prepare and store our food. Potentially making bacteria harder to kill is still a bad idea.