A Public Health Expert’s Ultimate Guide to Handwashing

Published on: Mar 13, 2024


Researchers estimate that one million deaths could be prevented annually if every person practiced proper hand hygiene. Handwashing is among the most effective tools one can use to avoid catching or spreading disease, yet research shows that handwashing is a skill imperfected by many. For example, a study done by the U.S Department of Agriculture (USDA) regarding hand washing before meals, revealed consumers fell short of adequate washing  97% of the time. Similarly, a study observing hand washing after bathroom use at various public attractions in major cities found as many as 15% of people omitted proper handwashing. Even handwashing studies done in medical centers have found adequate handwashing tendencies among hospital staff fall short of 100%. All of this research suggests that whether you are grabbing a bite to eat at your local eatery, exiting the bathroom of a crowded train station, or entering the operating room, it might be high time for some advice from an expert. 

Handwashing is a tried and true tool in the field of public health. Few laypeople beyond students of public health are privy to the origins of handwashing. Ignaz Semmelweis, a 19th-century Austrian physician, famously discovered that hand washing between work in the autopsy lab and the delivery room decreased the maternal mortality rate in his clinic significantly. Thus the link between the hands of health care workers and disease was born. Today, the Center for Disease Control (CDC) considers handwashing the most cost effective measure for reducing disease. Public health workers utilize handwashing as a tool in nearly every setting, whether it be a nation facing an epidemic of respiratory virus, a community facing a high burden of diarrheal disease, or a classroom attempting to mitigate absenteeism among students. You don’t have to deliver babies for your proper handwashing to make an impact. 

In this article, we will focus mainly on handwashing when ill, or preparing food and answer all the questions begged by someone ready to clean up their act.

The Science of Handwashing

Germs are everywhere, and human hands are a conduit for the exchange of pathogens. A man sneezes into his hand and touches the railing of a public staircase leaving an invisible germ, which a woman then touches and brings to her eyes, nose or mouth. Or, a cook uses the toilet, or handles raw meat, which often contains invisible amounts of animal feces, and fails to properly wash their hands, then prepares a meal to be eaten by restaurant goers. Germs are commonly spread by touching unwashed hands to your eyes, nose or mouth, as well as preparing or eating food with unwashed hands.

One gram of human feces can contain one trillion germs.  Most germs will not hurt you but certain germs are equipped with mutations for evading the human immune system, which may cause respiratory or diarrheal disease. Certain conditions can also cause germs to multiply in food or drinks, and this can cause illness. Harmful germs found in animal or human feces include Salmonella, E.coli O157, and norovirus which can lead to a diarrheal illness known as norovirus or spread respiratory infections such as adenovirus, and hand-foot-mouth disease. 

Handwashing with soap removes harmful germs from hands, and works by mitigating the spread of these germs from person to person or surfaces to people. Together soap and water lather, which causes the formation of micelles, small pockets that trap and remove germs from hands. When you rinse the lather, the trapped germs wash down the drain. 

The link between handwashing and the reduction of pathogenic bacteria in hands and reducing infection rates in various settings is well established.  The CDC reports that handwashing education reduces the number of people who get sick with diarrhea by 23-40%, reduces respiratory illnesses in the general population by 16-21%, and reduces absenteeism due to gastrointestinal illness in school children by 29-57%.

Proper Handwashing Techniques

Handwashing Steps: A How To:

The CDC outlines five steps for proper hand washing. All of which are broken down below:

    1. “Wet your hands with clean, running water (warm or cold), turn off the tap, and apply soap.” Running water is important because hand washing in standing water allows for recontamination of your hands. The temperature of the water has shown no observable difference in microbe removal when comparing cold, or warm water. Lastly, using soap and water is essential to effectiveness because the surfactants in soap work to lift microbes from the skin, and encourages more thorough scrubbing.

    1. “Lather your hands by rubbing them together with the soap. Lather the backs of your hands, between your fingers, and under your nails.” Friction is created through scrubbing and lathering, which aids in lifting germs from the skin. Microbes are more highly concentrated under the nails, but are present across the entire surface of the hand. 

      When deciding what to lather with, it should be noted that antibacterial soaps have not been found to be any more effective than plain soaps, with the exception of studies done in health care settings. Moreover, antibacterial soaps have been linked to antibiotic resistance. The Food and Drug Administration (FDA) recommends lathering with plain soap and water.

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

    1. “Rinse your hands well under clean, running water.” Soap, and friction caused by lathering and scrubbing lifts the germs to then be rinsed off the hands. Rinsing soap off of your hands has also been found to minimize skin irritation.

    1. “Dry your hands using a clean towel or an air dryer.”  Hands should be dried after washing because wet hands transfer germs more easily. Studies show that best practice is to use a clean towel or to air dry hands.

The World Health Organization (WHO) and the Center for Disease Control (CDC) offer a number of handwashing videos that provide a helpful visual tool when practicing proper handwashing technique.

Soap vs Hand Sanitizer

Soap and water are the most effective way to wash your hands, but when this is not feasible hand sanitizer can be used. Hand sanitizers should be alcohol-based and contain at least 60% alcohol. Studies have found that hand sanitizers with alcohol concentration lower than 60-95%, or non-alcohol-based hand sanitizers are not as effective at killing germs when compared to those with higher concentrations of alcohol. Hand sanitizers with lower concentrations may not work on all harmful germs, or will simply reduce the growth of certain germs instead of killing them. 

While hand sanitizer is better than nothing, it does not eliminate all the germs and can be less effective when hands have visible dirt or grease on them. Hand sanitizers have been shown to be effective in clinical settings, where hands are often exposed to germs but not grease or soil.  However, Hand sanitizer works less well for greasy or soiled hands, such as after people handle food, or work in the garden. In these circumstances handwashing with soap and water is recommended. 

Hand sanitizer may also be less effective for removing harmful chemicals from your hands when compared to washing with soap and water. Hand sanitizers cannot remove or inactivate some harmful chemicals such as pesticides, and studies have shown higher levels of pesticides in the bodies of people who reported using hand sanitizer to clean their hands.

Handwashing in Food Preparation

Hand washing is very important when cooking and handling food. Several food outbreak investigations have implicated the hands of food workers as the source of pathogens for the contaminated foods. In a study of 816 foodborne outbreaks, the most commonly reported factor concerning the infected food worker’s involvement was direct contact with food using bare hands, followed by inadequate hand washing, and cross contamination from contaminated raw ingredients to ready to eat food. In this section we will delve into specific moments during food preparation when washing hands should occur, and also cross-contamination and other things to consider when preparing foods for yourself or others. 

So, you are making a meal for yourself or others. When should you be washing your hands? There are specific moments during food preparation, where washing hands is recommended to avoid spreading pathogens from your hands to your meal. The CDC recommends washing your hands before, during, and after preparing food. Moreover, you should wash your hands after handling certain foods such as uncooked meat, chicken or other poultry, seafood, flour or eggs. You should also wash your hands after touching garbage or wiping any surfaces with cleaning chemicals. Lastly, it is important to wash hands after touching pets, or pet food, after using the bathroom, and post coughing, sneezing or blowing your nose. 

Cross-contamination is another important consideration when safely preparing food for yourself or others. Cross-contamination occurs when harmful bacteria are physically moved from one person, object or place to another. When it comes to preventing foodborne illness, cross contamination is a key factor to consider. Avoiding cross contamination requires that you clean hands and surfaces often, as harmful bacteria can spread throughout the kitchen and can make its way to utensils and countertops. Washing hands with soap and water at the above junctions is essential for avoiding cross contamination.

Handwashing When Sick

Handwashing when you are ill is especially important, as washing hands after coughing and sneezing is essential for mitigating the spread of illness. The CDC reports that handwashing can reduce the risk of respiratory illnesses such as the common cold by nearly 20%, and can reduce the risk of diarrheal diseases among people with weaker immune systems by almost 60%. Despite this, according to an American Cleaning Association survey, only 26% of Americans always wash their hands after sneezing. This survey also found that women were more likely than men to wash their hands after coughing or sneezing. The study found that 51% of men seldom or never washed after coughing or sneezing compared to 29% of women. These numbers suggest a refresher in best practice hand hygiene when sick or caring for someone who is sick is in order.

When ill, it is important to wash hands frequently such as after coughing or sneezing, or after touching your nose, mouth or eyes. The practice of handwashing, when you or someone you are caring for is sick, is essential to avoiding the spread of harmful bacteria.  When caring for others, maintaining best practice handwashing as described in the rest of this article remains very important. The CDC recommends washing hands before and after caring for someone who is sick with vomiting or diarrhea. Handwashing is also recommended before and after treating cuts, sores, or wounds on yourself or others.

When to Wash Your Hands

It may not come as a surprise that key moments for hand washing include before meals and after restroom use. However in addition to these, there are some scenarios where handwashing is commonly overlooked. A study done in Hong Kong found that 91% of people washed their hands after coming into contact with fecal matter. This instance seems intuitive, however, in other instances, percentages decreased. For example, only 62% of people reported washing their hands after contact with animals or pets, and only 17% of people reported washing their hands after touching “public installations or equipment”. The Center for Health Protection, an entity in China, similar to the US’s CDC, recommends 8 instances where hand washing should occur.

They are as follows: 

  1. After coming in contact with vomit or fecal matter.

  2. After using the toilet

  3. Before and after visiting medical centers, or caring for the sick 

  4. After contact with animals, including pets

  5. After touching “public installations or equipment”

  6. Before eating or handling food 

  7. After coughing or sneezing

  8. Before touching eyes, nose, and mouth

Follow these guidelines to avoid commonly overlooked instances where hand washing should occur. 

Hand Hygiene for Children

Parents and caregivers play a crucial role in teaching children hand hygiene. It is essential to start implementing best practice hand washing techniques early. Teaching kids the 5 basic hand washing steps as described by the CDC, wet, lather, scrub, rinse, dry, is a great place to start. Moreover, it's important to teach children when hand washing is necessary such as after using the bathroom, or before eating.

Making hand washing fun is a great way to encourage best practice hand hygiene among children. You can do so by creating a handwashing song, or making it a game. The CDC provides an animated hand-washing video that can be a helpful tool when teaching children proper handwashing technique. Another important thing to remember when teaching children about hand washing is that frequent reminders are important. Leading by example is another great way to encourage hand washing for children. The CDC suggests making handwashing a part of your routine, and setting a positive handwashing example for your child. Your child can take this healthy habit with them as they grow into adulthood, and continue to practice it throughout their lifetime.

Hand Hygiene in Public Settings

Hand hygiene is especially important in public spaces. As mentioned before, a study done in Hong Kong found that only 17% of people reported washing their hands after touching “public installations or equipment”. Public hotspots for germs include touch screens, gym equipment, restaurant menus, water fountains, shopping carts, elevator buttons, ATMs, and so much more. While soap and water may not be available in all public spaces, an alcohol-based hand sanitizer with an alcohol content of over 60% is a great alternative in lieu of these resources.

Businesses and institutions, such as schools or education institutions can play a part in encouraging hand hygiene in public spaces. They can do so by building time into daily routines for handwashing. Moreover, institutions can work to increase access to hand washing infrastructure such as sinks, soap dispensers and portable hand washing stations, as well as providing resources for drying hands such as paper towels and hand dryers. Additionally, visual cues such as hand washing posters or stickers can be placed in businesses or schools to promote hand hygiene. Lastly, hand sanitizers with greater than 60% alcohol can be provided by businesses or institutions.

Hand Care and Skin Health

Frequent handwashing is important, but it can also impact your skin. The American Academy for Dermatology explains that regular hand washing can dry your skin. Frequent exposure to soaps strips the outer layer of your skin of oils, and can diminish the healthy fatty compounds in the top layers of the skin. This can lead to cracks in the skin barrier, and lead to increased risk of superficial skin infections. Moist unbroken skin is better protected from germs.
Dryness and irritation can be prevented. Washing your hands with cool or lukewarm water can help as extremely hot water can irritate skin. Patting your hands dry with a clean towel, and avoiding rough rubbing can also minimize skin breakage. Lastly, applying hand cream or ointment can decrease irritation and help prevent dryness. Some recommended ingredients to look for in a moisturizer include petroleum, mineral oil, ceramides, or glycerin. When looking for a moisturizer it's important to consider thickness. A lotion with a thicker consistency will be more moisturizing, compared to a thinner lotion which contains more water and would be recommended for very dry skin.

The Future of Hand Hygiene

Hand washing remains extremely important for the health of communities across the globe. Amidst the COVID-19 pandemic handwashing was an integral tool for protecting yourself and preventing the spread of disease. In 2020, 70% of people used basic hygiene services across the globe, and studies show that handwashing practices have picked up since the pandemic. The pandemic garnered a lot of attention towards hand washing, but best practice handwashing remains important for preventing the spread of all diseases, and must be sustained. 

Moreover, as antimicrobial resistance reaches the forefront of public health concerns, hand washing may be more critical than ever. As some antibiotics become less useful for treating bacterial infections, handwashing remains a great way to prevent the spread of harmful bacteria, and ultimately disease. Hand washing saves lives, and proper handwashing techniques will keep you and your communities safe. Whether you’re entering the operating room, or maybe just the classroom - it’s time to hit the sink!


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About the Authors

Written by:

Jessica Weissman

Jessica Weissman is a Masters student at Columbia University Mailman School of Public Health. At Mailman she studies in the Sociomedical Sciences Department and is pursuing a certificate in Sexuality, Sexual and Reproductive Health. Jess is interested in reducing health disparities for sexual and gender minority populations. Jessica holds a Bachelor of Science in Public Health from the University of Massachusetts Amherst.

jess weissman headshot

Jessica Weissman

Contributing Author

Education: Columbia University Mailman School of Public Health

Reviewed by:

Katherine Paul, MPH

Katherine Paul, MPH is a senior project manager at a leading medical communications and publications organization. She supports multidisciplinary teams handling large-scale accounts, the deliverables of which improve health outcomes and patient well-being. Ms. Paul holds a Master of Public Health (MPH) degree in Health Promotion from Columbia University, Mailman School of Public Health and passed the Certified Health Education Specialist (CHES) shortly after graduation. She holds a Bachelor of Arts degree in Sociology from Dickinson College.

Ms. Paul previously worked at a public health non-profit where she managed all aspects of diverse health-related projects, including the implementation of a randomized controlled clinical trial on sexual health for teens with developmental disabilities, as well as the evaluation of a statewide tobacco cessation program with more than 20,000 annual cases. She has developed and delivered posters and presentations at national conferences including the American Public Health Association (APHA) annual meeting. 

Opinions and information published by the author here on MastersPublicHealth.com are of my own and do not necessarily represent the views or opinions of my employer or other organizations for my designated roles.

Katherine Paul

Katherine Paul, MPH

Editorial Lead

Education: Columbia University, Mailman School of Public Health

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