Web Zap*Germs Archive

March 21, 2006

Not All Antiseptic Hand Gels Kill Germs

A surprising discovery has been published in Emerging Infectious Diseases: alcohol-based hand gels with less than 60% alcohol can't be counted on to kill most harmful bacteria and viruses.

Based on experiments that found an alcohol concentration of 60% or more was needed, a team led by Scott Reynolds (a specialist in infection control at the James H. Quillen Veterans Affairs Medical Center in Mountain Home, Tennessee) found that a number of antiseptic gels sold in US stores had alcohol concentrations below 60%.
In the fall of 2005, a...survey of 18 retail chains (supermarkets, drug stores, general retailers, specialty shops) uncovered a substandard product at all 3 stores of 1 deep-discount chain. The marketing profile of deep-discount chains suggests that poorer segments of the population may be more at risk of purchasing inadequate antiseptic gels. Moreover, 40% ethanol products may be stockpiled in homes and offices.
Reynolds' group was smart enough to run some e-commerce checks, as well:
An extensive Internet survey identified no additional substandard commercial products. However, the alcohol content of less-common brands was not always available online, and several Internet sites provide recipes for a bubble gum–scented children's hand sanitizer that contains 33% isopropanol as the sole active ingredient.
So the smart thing to do is to check the label of any alcohol sanitizing gel, to be sure it has at least 60% alcohol.

The NYT noticed and reported on Reynolds' findings. Their article included this detail on Reynolds' experimental methodology:
Mr. Reynolds had the [East Tennessee State University biology-class] students place their hands on agar plates of growth medium before and after one of several experimental conditions: rubbing their hands briskly under tap water; sudsing with hospital-grade soap and then rinsing with water; or rubbing their hands with a dollop of one of two types of alcohol-based hand sanitizer. The sanitizers used were a foam version from the hospital that contained 62 percent ethanol, and a gel version Mr. Reynolds's wife bought at a local discount store.

The next day, much to Mr. Reynolds's surprise, the culture plates from hands doused and rubbed with the store-bought gel were covered with clumps of bacteria that had, in some cases, formed a visible outline of the student's handprint on the plate.

Only when he flipped the bottle around to read the label on the back did Mr. Reynolds see that the gel's active ingredient was "40 percent ethyl alcohol."

"Otherwise, it looked like all the rest you see in the store," he said. "Same price. Same claims. Same pump bottle."

In a more formal follow-up study, Mr. Reynolds and two colleagues replicated the results, and confirmed that the lack of sufficient alcohol was to blame. If anything, he said, the faulty gel seemed to mobilize the bacteria, spreading them around the hand instead of killing them.
Allison Aiello is an epidemiologist at the University of Michigan who has studied the use and relative effectiveness of alcohol-based gels and antibacterial soaps. She offered some practical advice on when and how to use the alcohol gels:
"Studies show that the computer keyboard, the phone receiver, and the desk are worse than the bathroom in terms of micro-organisms," she said. "Washing with plain old soap and water should be your first choice. But if you're stuck between meetings and about to grab lunch at your desk, or just use somebody else's keyboard, using a hand sanitizer before and after could be a really good idea."

How much goop should you use? Vigorously rub all sides of your hands with enough gel or foam to get them wet, and rub them together until they are dry. If your hands are dry within 10 or 15 seconds, according to the C.D.C. guidelines for health care workers, you haven't used enough.


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