Does water temperature have any significance when washing hands? Does the soap type?
The Rutgers University scientists contaminated the hands of volunteers with harmless bacteria and made them wash hands with water at 38℃, 25℃ and 15℃. Scientists have estimated that 15℃ is the lowest water temperature at which people would feel comfortable washing hands. USPH require the water in the food preparation facilities has a temperature of at least 100℉ (or 38℃).
Historically, most people have been taught to wash hands with the hottest water they can stand. Generally, people associate warmer water with cleaner hands. However, the study found that there was next to no link in doing so. Water temperature has no effect. And this is not the only study with a similar result - almost identical conclusion is reached in a 2002 Food Service Technology publication.
In recent years, it has been repeatedly found that antibacterial soaps have no benefit either. They do not clean better than ordinary ones. On the contrary, in the long run, they can do harm, making bacteria more resistant.
What makes your hands cleaner, then? It turns out only the time we spend on washing.
The researchers from Rutgers have decided to draw attention to the time the volunteers foam their hands with soap - 5, 10, 20 and 40 seconds respectively, without rinsing. They found a significant statistical difference between 5 and 20 seconds’ results, but not between the remaining intervals. In other words, 5 seconds are not enough. It takes between 10 and 20 seconds of soap to wash your hands well.
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