Tag Archives: hygiene

The Efficacy of Hand Sanitizers

Given their prevalence in offices, hospitals and pharmacies (how naïve?), I would have thought the effectiveness of hand sanitizers would have been a lot greater than it is:

In 2005, Boston-based doctors published the very first clinical trial of alcohol-based hand sanitizers in homes and enrolled about 300 families with young children in day care. For five months, half the families got free hand sanitizer and a “vigorous hand-hygiene” curriculum. But the spread of respiratory infections in homes didn’t budge. […] A Columbia University study also found no reduction in common infections among inner-city families given free antibacterial hand soap, detergent, and cleaning supplies. The same year, University of Michigan epidemiologist Allison Aiello summarized data on hand hygiene for the FDA and pointed out that three out of four studies showed that alcohol-based hand sanitizers didn’t prevent respiratory infections. Then, in 2008, the Boston group repeated the study—this time in elementary schools. […] Again, the rate of respiratory infections remained unchanged, though the rate of gastrointestinal infections, which are less common than respiratory infections, did fall slightly. Finally, last October, a report ordered by the Public Health Agency of Canada concluded that there is no good evidence that vigorous hand hygiene practices prevent flu transmission.

The final advice:

Follow the data and get a flu shot, wash your hands sensibly after using the bathroom and around meals, and stop wasting money on hand sanitizers.

via Link Banana, saying “they could (should) have been most explicit on the differences between hand washing […] and hand sanitizers”. Seconded–I’m no longer sure where hand washing fits in this picture.

Note: The Wikipedia article for hand sanitizers paints them in a slightly more positive light, but with many caveats (e.g. alcohol content and duration of exposure to the product is important, etc.).

Paper Towels vs. Hand Driers

Fully accepting his bias, Paul Revere looks at the evidence in the long-standing paper towel–hand drier debate and finds in favour of the humble paper towel.

There were four parts to the study: Part A looked at the drying efficiency of hand drying method; Part B involved counting the number of different types of bacteria on the hands before and after drying; Part C studied the potential contamination of other users and the washroom environment; and Part D took a bacterial sampling of Dyson Airblade dryers in public washrooms.

Paper towels and the Dyson Airblade were found to be equally efficient at drying hands, each achieving 90% dryness in approximately 10sec. However, the warm air dryer was considerably less efficient, taking 47sec to achieve the same level of dryness. […]

Paper towels were found to reduce the number of all types of bacteria on the fingerpads by up to 76% and on the palms by up to 77%. By comparison, the Dyson Airblade increased the numbers of most types of bacteria on the fingerpads by 42% and on the palms by 15%. However, after washing and drying hands under the warm air dryer, the total number of bacteria increased by 194% on the fingerpads and on the palms by 254%.

The Dyson Airblade performed less well than paper towels and the warm air dryer in Part C in which the hands of 10 subjects were artificially contaminated with yeast suspension. During use, open agar plates were placed at 0.25m intervals from the hand-drying device up to a maximum of 2m. Yeast colonies that grew on the plates were counted.

The Dyson Airblade dispersed potential contamination to other users and the washroom environment to a distance of at least two metres, whereas paper towels spread contamination 0.50m and the warm air dryer 0.25m.

Part D showed that the Dyson Airblade dryers in the public washroom sampled were contaminated with large numbers of bacteria, including potential pathogens such as E. coli, staphylococcus and pseudomonas aeruginosa, particularly the bottom of the hand drying chamber

According to Keith Redway, senior academic in the department of Biomedical Sciences at the University of Westminster: “The results of all parts of this study suggest that the use of warm air dryers and jet air dryers should be carefully considered in locations where hygiene is of paramount importance, such as hospitals, clinics, kitchens and other food preparation areas, schools, nurseries and care homes.” (Clean Room Technology [UK])

I have odd hand washing habits in public bathrooms and have my own preferences:

  • Paper towels preferred if there are doors to open on exiting the bathroom. This is because many users of public bathrooms do not wash their hands, and I don’t want to re-contaminate my hands after washing and drying–I’ll use a paper towel to open the door.
  • The Dyson Airblade in all other circumstances.

Odd habits, admittedly, and habits that are unlikely to change given these findings… mainly because the research was funded by the European Tissue Symposium.

via Marginal Revolution

Children Exposed to ‘Dirt’, Healthier

From the ‘Science proves mum right’ and ‘Obvious, but still needs to be stated’ file comes the news that children who are exposed to bacteria, viruses, worms, and dirt have healthier immune systems.

Public health measures like cleaning up contaminated water and food have saved the lives of countless children, but they “also eliminated exposure to many organisms that are probably good for us.”

“Children raised in an ultraclean environment, […] are not being exposed to organisms that help them develop appropriate immune regulatory circuits.”

Of course there are caveats, or at least common sense rules (although even the researchers in this field are debating exactly how far to take this):

“I certainly recommend washing your hands after using the bathroom, before eating, after changing a diaper, before and after handling food,” and whenever they’re visibly soiled, [one researcher] wrote.

Dr. Weinstock goes even further. “Children should be allowed to go barefoot in the dirt, play in the dirt, and not have to wash their hands when they come in to eat.”

via Kottke

Selling Hand-Washing to Africa

The New York Times on how Dr Val Curtis ‘sold’ hand-washing to Africa:

Diseases and disorders caused by dirty hands — like diarrhoea — kill a child somewhere in the world about every 15 seconds, and about half those deaths could be prevented with the regular use of soap, studies indicate.

But getting people into a soap habit, it turns out, is surprisingly hard.

To overcome this hurdle, Dr. Curtis called on three top consumer goods companies to find out how to sell hand-washing the same way they sell Speed Stick deodorant and Pringles potato chips.