The most effective way to wash your hands

Your hands are constantly getting bacteria and viruses from basically everywhere and everything. Have you thought about how contaminated your phone or laptop’s keyboard is? A lot! Now, think in public surfaces such as door handles, paper towels at toilets, credit cards or cash. And what about shaking hands when greeting someone?

Microbes are found everywhere but, luckily, most are not harmful to humans. There are, however, some bacteria that are potential pathogens for us. We need to adopt cleaning measures in order to eliminate bacteria as much as possible, thus, reducing the chances of getting sick.

Sterilization Vs Disinfection

First of all, it is worth knowing how these two methods work on destroying bacterial cells and what is the difference between them.

• Both methods occur at a molecular level and require the gain or loss of electrons (oxidation and reduction, respectively), which act on the different cell components (DNA, RNA, proteins and lipids).
• These processes happen immediately.
• Sterilization eliminates completely all forms of microbial life, including endospores. Sterilization methods include the autoclave and incineration.
• Disinfection kills bacteria but does not remove endospores. Disinfectants include oxidizing agents (bleach and hydrogen peroxide) and coagulating agents (alcohol, biguanides, aldehydes).1

How Well Does Handwashing Reduce The Bacterial Load?

One of the most important steps we can make to avoid getting sick and spreading germs to others is to wash our hands regularly.2 Commonly, we have two options:

• Regular soaps work by chemically breaking down the oil of the hands. Friction by rubbing hands also breaks down the oil mechanically. The more soap and the longer the hands are rubbed together, after flashing with water, the less oil and microbes will be left. Bacteria on the skin are not killed, but instead, flushed away.
• Antibacterial soaps contain some type of antibacterial substance, such as alcohol (concentration at higher than 60%) or benzalkonium chloride. These soaps kill many types of bacteria, but not all. There is no evidence that antibacterial soaps are more effective at handwashing than regular soaps.3 Moreover, overuse of these soaps can reduce the number of healthy bacteria of the skin.4

Alcohol is used as an antiseptic at 60-80% concentration. The reason it cannot be used at a higher concentration is that the coagulation of the bacterial cell wall is excessive and the disinfectant cannot enter the cell. Moreover, because of its ability to evaporate water, an alcohol solution of 100% is harmful to the skin. 

The reason why it comes in a gel form for hand sanitization is to prolong the contact time of microorganisms with alcohol by slowing the evaporation.1

One study with 20 volunteers compared bacterial reduction after handwashing with water, water with non-antibacterial soap and no washing. They proved that handwashing with water and soap is more effective than with water alone to reduce the number of bacteria from faecal origin. This is a useful measure for the prevention of transmission of diarrhoeal diseases.5

However, another study showed that soap does not seem to eliminate all bacteria from your hands. It was done in health care professionals and volunteers, and assessed how effective was handwashing with soap to remove Staphylococcus aureus.6 S. aureus is a bacterium that lives on the skin and the nose of about 30% of healthy people without causing infection. However, S. aureus is a common pathogen that can cause infections, especially if the skin breaks (due to a cut or wound).7 It appears that washing hands alone with soap did not remove all the S. aureus. Instead, they were completely removed by a 4% chlorhexidine detergent scrub and alcoholic solutions. This study highlights the importance of wearing gloves in the laboratory and health care environment.⁶

In summary, there seems to be an agreement that handwashing with regular soap for at least 15 seconds, is highly effective at removing most, but not all, bacteria.8  When water is not available, antibacterial soaps can be a useful alternative.3

How Well Do We Need To Clean Our Fruits And Vegetables?

As a safety measure and to reduce the number of microorganisms in the food we buy, we often are told to clean with water vegetables and fruits.

Does washing with water really eliminate all bacteria?

One study showed that bacterial loads were not significantly reduced by washing in a water bath or by gentle water flow (2 L/min). Only at a higher washing flow (8 L/mins) yielded significant reductions. This indicated that the detachment of bacteria is dependent on the mechanical force that is applied, and on whether the cells are alive or dead.11

Another study shows that soaking and washing with tap water does not completely reduce all bacteria in vegetables and fruits.12

Should we also clean ready-to-eat salads?

It looks like ready-to-eat salads are often contaminated by bacteria during the handling process, and sometimes even harbour higher amounts of bacteria (including several potential harmful species) than non-processed vegetables. This is thought to happen due to physical damage of the vegetables, which enhances microbial growth.9, 10, 11

So what would be the best method?

Peeling, soaking in water with a few drops of bleach or with a 0.1% potassium permanganate solution13 seems to kill the most bacteria. 

And what about pesticides and other residues?

Studies have shown that washing fruits and vegetables in a baking soda solution for 15 minutes, remove pesticides, contaminants and other surface substances.¹⁴

Take away message

Handwashing with soap is actually very necessary to remove most of the bacteria that you pick up throughout the day. You should aim to rub your hands for at least for 15 seconds.

To remove most bacteria from fresh vegetables and fruits, you should thoroughly flush with tap water for a couple of times. The more, the better. And if you are worried about the pesticides, you can wash them for 15 minutes in a baking soda solution.