Noyes News and Events

December 10, 2017

The Science behind Hand Washing

“Dinner time – go wash your hands.”  I can still hear my mother’s voice yelling out those words as she rounded up the troops for the evening meal.  Turns out Mom’s command was also good advice. Hand washing is the single best thing you can do at the front lines of daily life to keep healthy.  Studies show that handwashing can prevent 1 in 3 diarrhea-related sicknesses and 1 in 5 respiratory infections such as cold or the flu.   

How do germs spread?  Many times, small amounts of fecal matter (poop) are to blame.  According to the CDC, human and animal feces is an important source of germs like Salmonella, E. coli O157, and norovirus that cause diarrhea, and it can spread some respiratory infections like adenovirus and hand-foot-mouth disease. These kinds of germs can get onto hands after people use the toilet or change a diaper, but also in less obvious ways, like after handling raw meats that have invisible amounts of animal poop on them. A single gram of human feces — about the weight of a paper clip—can contain one trillion germs. Germs can also get onto hands if people touch any object that has germs on it because someone coughed or sneezed on it. When these germs get onto hands and are not washed off, they can be passed from person to person. Moreover, people frequently touch their eyes, nose, and mouth without even realizing it and this action allows germs to enter the body, which can then make a person ill.

While the average healthy person has a robust immune system capable of dealing with a bit of dirt, it is still imperative to wash hands often.  In addition, the most susceptible, the very young, the elderly, and individuals with weakened immune systems, should make a distinct effort to include excellent hand hygiene as part of their daily routine. Medical professionals recommend washing hands:

  • Before, during, and after preparing food

  • Before eating food

  • Before and after caring for someone who is sick

  • Before and after treating a cut or wound

  • After using the toilet

  • After changing diapers or cleaning up after another person who has used the toilet.

  • After blowing your nose, coughing, or sneezing

  • After touching an animal, animal feed, or animal waste

  • After handling pet food or pet treats

  • After touching garbage

Per the above list, our hands encounter a treasure trove of microbes and pathogens every day.  Microbes are all tiny living organisms that may or may not cause disease.  Germs, or pathogens, are types of microbes that can cause disease. Hand washing washes the bad guys down the drain.  

How to Wash Your Hands How should

  1. Wet your hands with clean, running water (warm or cold), turn off the tap, and apply soap. Studies show that cold water works as effectively as warm water.

  2. Lather your hands by rubbing them together with the soap. Be sure to lather the backs of your hands, between your fingers, and under your nails.

  3. Scrub your hands for at least 20 seconds. Need a timer? Hum the “Happy Birthday” song from beginning to end twice.  Evidence suggests that washing hands for about 15-30 seconds removes more germs from hands than washing for shorter periods.

  4. Rinse your hands well under clean, running water. Watering needs to be running – don’t rinse in a sink of standing water as hands may be recontaminated with the dirty rinse water.

  5. Dry your hands using a clean towel or air-dry them.

Washing hands with soap and water is the best way to reduce the number of germs on them in most situations. If soap and water are not available, use an alcohol-based hand sanitizer that contains at least 60% alcohol.  Alcohol sanitizers do not eliminate all types of germs and might not remove harmful chemicals.  Keep in mind; hand sanitizers are not as effective when hands are visibly dirty or greasy.

Handwashing is a highly effective way to prevent illness.  Studies show that handwashing alone:

  • Reduces the number of people who get sick with diarrhea by 31%.

  • Reduces diarrheal illness in people with weakened immune systems by 58%.

  • Reduces respiratory illnesses, like colds, in the general population by 16-21%.

For more information on handwashing, visit:  

Lorraine Wichtowski is a community health educator at UR Medicine Noyes Health.  If you have questions or suggestions for future articles, contact Lorraine at or (585) 335-4327.