Emily Oster

8 min Read Emily Oster

Emily Oster

Yes, You Really Do Need to Wash Your Hands

The history, impact, and behavior behind hand washing

Emily Oster

8 min Read

I noticed recently that I mention hand washing a lot. Usually in a somewhat incidental way — Of course, the only thing that really helps to prevent the spread of norovirus is washing your hands or If you have visitors to your newborn, make sure they wash their hands. 

In fact, hand washing isn’t just an afterthought. It deserves its own article. Today:

  • The (brief) history of hand washing 
  • What we know about the impact on disease, especially in little kids
  • How to get people to wash their hands (adults and children) 

Spoiler on the last point is that it is hard to get people to wash their hands. Sorry!

History of hand washing

(For a much longer history, I recommend this excellent article.) 

Historically, prior to the mid-1800s and even a bit past that, people were extremely resistant to the idea that washing hands would be related to disease. Sure, they washed their hands, but mostly related to religious rituals. For the most part, the idea that hygiene would have a benefit in medicine was not just ignored but actively shunned.

baby hand washing with parent
PNW Production / PNW Production

There were exceptions. Moses Maimonides — who died in 1204 — was a proponent of hand washing after dealing with sick patients or when he got off his horse. But overall, doctors for centuries seemed to take this idea as ridiculous. A substantial cause of maternal mortality was doctors who dealt with corpses and then immediately came to deliver a baby, without any hand washing. This introduced bacteria and, many times, killed the woman (this was before penicillin as well). During this period, midwives had a much better survival rate, simply because they focused only on deliveries.

In the mid-1800s, several people ultimately turned the tide on hand washing: Oliver Wendell Holmes, a Hungarian doctor named Ignáz Fülöp Semmelweis, and Florence Nightingale, who trained her nurses to wash their hands and faces, among other reforms. To be clear, despite empirical proof of their claims, there were haters. Semmelweis refused to publish his findings showing that hand washing saved lives for fear of ridicule. As the germ theory of disease developed, hand washing became accepted as important in medicine. And, of course, beyond.

Hand washing and kids’ diseases

The initial evidence about the importance of hand washing was based on medical settings. It’s very clear, given our understanding of germ theory, why hand washing would prevent disease in this case. Treating disease requires close contact with sick patients — patients who carry bacteria or viruses in many cases. Transiting between patients, it is easy to carry those germs to another patient. Hand washing kills these germs, hence it helps.

By extension, we might think that hand washing would prevent the spread of illness in non-medical settings, like your home, or school, or day care. A core question in those settings is How much spread is prevented? The answer will depend on how good people are on average at adhering to hand washing, as well as how important this particular avenue of spread is. In day care, kids spread germs in many ways — sharing snacks, licking faces — so, unlike in a medical setting, it’s less controlled.

Nevertheless, the data shows that hand-washing interventions in child care settings can dramatically decrease the incidence of gastrointestinal viruses. In a meta-analysis, hand-washing interventions in child care settings in high-income countries decreased diarrhea incidence by 30%. Diarrhea is the primary focus of studies on this, although there is some evidence from other child care settings of a reduction in norovirus with enhanced hand hygiene. 

It is more challenging to study household transmission and the role of hand hygiene. What seems clear — again, based on the science — is that if someone in the household has a stomach illness, hand washing should somewhat lessen the chance of it spreading to others. In the case of norovirus, for example: it is spread through inhaling or ingesting the virus from the affected person. If you clean vomit off a child, germs are on your hands, and if you wash them carefully afterward, you could (I emphasize could) save yourself. 

Hand washing, in contrast, is likely to play a more limited role in the spread of respiratory illnesses, which are more likely to be spread airborne or through sneezing or coughing in the face of other people. This isn’t to say there is no role, but the impacts are certainly smaller.

Conclusion: Hand washing is known to be very important in medical settings for a number of infection-control reasons. In community settings, there appear to be large impacts on diarrhea in particular. It should also be noted that hand washing carries no risks (other than dry skin) and is inexpensive. It’s a no-brainer! A basically free intervention that makes you smell better and makes everyone around you less sick.

The only problem is: it’s very hard to get people to do it.

Hand-washing interventions

Compliance with hand washing is not perfect — honestly, it’s not even that good. This study, which is pretty depressing, is a review of other studies on hand-washing compliance in the intensive care unit. Forget about at your child’s day care center; these are studies in medical settings. The studies generally observe, either overtly or secretly, medical provider behavior and compare their hand-washing behavior with what is suggested by the World Health Organization as the gold standard.

Focusing only on higher-income countries, only 65% of health care providers adhered to the guidelines. These numbers were higher for infant and pediatrics ICUs relative to adult facilities (which I guess is encouraging) and higher for nurses than doctors. (These numbers are far, far worse in lower-income countries, for reasons of access. That’s an important policy priority, but not what I want to focus on today.) 

If this is what is happening in the ICU, is it any wonder that we do not have high compliance in child care settings, or in our own homes? If your doctor might not be washing their hands, how can you be surprised when your 9-year-old comes out of the bathroom insisting they washed their hands, which you can clearly see they did not by the dry sink and towel.

The question is: how to get more hand washing? 

The answer is: we don’t know. Information campaigns might have some effect, but low compliance persists even in settings like hospitals where the value is known. This is something hand washing has in common with many other positive health behaviors, like eating vegetables and exercising. People know they should do it, but for some reason they do not. Hand washing is annoying, it takes time, it’s easier not to do. One interesting intervention in a school in Pakistan tried to motivate children by teaching them about germs and showing them germs on their hands with a special light. This achieved a short-term increase in hand washing but nothing sustained. 

Making hand washing easier and more accessible is also thought to be helpful, though, again, far from a silver bullet. 

Some success has been found with so-called “nudges” — basically, reminders in the moment, in various forms. This paper summarizes several of those. They are mostly focused on bathrooms — how do you get people to wash their hands when leaving the toilet? Options include threatening messages, encouraging messages, pictures of eyes watching you (since people are more likely to wash their hands if someone else is in the room with them), signs on the floor to show you how to walk to the sink, and so on. The effects of these interventions were mostly small: a 20%, 30% increase in hand washing, and it’s hard to know what to make of some of the results (male eyes matter, female eyes do not for some reason?). So, something, but underwhelming.

I wish this last paragraph said some version of “The magic bullet is…” But it does not. In writing this post, I had all kinds of creative ideas, which I’m sure you can add to. Things like telling kids that you installed a special sensor in the bathroom door that will sound an alarm if it detects germs on their hands (good idea until they try to test you). Or toilet paper with a light coating of purple dust that comes off on your hands (good idea but doesn’t work for men peeing). The problem is it’s not just bathrooms — we really want people to wash their hands regularly, and that’s simply hard. 

The bottom line

The dubious history of hand washing and its underuse even in the modern day are probably a reflection of the same basic issue. When people wash their hands, nothing happens. I mean, things happen — reductions in germs that lead to less illness! But nothing visual happens, and the benefits for illness prevention appear later and disconnected. We do not get the dopamine hit of success or positive reinforcement that might keep us coming back. 

And yet: we should continue to try. With reminders and nagging. In the words of the authors of this work on the history of hand washing, “The forerunners of handwashing were met with nothing but ignorance and mockery. Let us try to improve our hand hygiene and think about them as we wash our hands.”

6 Comments
Inline Feedbacks
View all comments
TheCosmicTeamA
TheCosmicTeamA
17 days ago

Buy two agar plates (to grow cultures, can get cheap on the Internet). Have your kids come home from school and put their hands on one. Then, thoroughly wash and dry hands on a clean towel and have them put hands on the other. Wait for about four days. You’ll be completely convinced!

katmon
katmon
18 days ago

I shared with my husband – since we bicker about this – and he quipped, “What she didn’t say is, ‘How much hand washing is needed to make it effective’… like do we get 80% of the benefits when just rinsing with water? Or only 20% and we must always use soap for any substantial effect? Is 5 seconds sufficient if there is soap? 20s?”

kate9
20 days ago

I am a biologist (cancer) with a hobbyist’s interest in issues of the microbiome and hygiene theory. Hand washing is actually a pretty complex. I think than the main takeaways are antibacterial products are nearly always ineffective or actively harmful and should be avoided. Alcohol based sanitizers can be really good if they are used in a situation that you are dealing with immunocompromised people and nasty germs like a healthcare worker. Healthcare, childcare and food prep workers should be very careful of their skin health because damaged skin can actually shed more bacteria (most of the bacterial that you pass on from your skin is attached to shed skin flakes, more damaged skin, more shedding). Handwashing and bathing in general has little effect on your established skin microbiome but can remove transient bacteria. So the main point: if you are handling poop or vomit, wash your hands! If you aren’t, you can probably relax and make sure you aren’t washing so much as to damage your skin because your healthy skin layers and microbiome are also doing a big job to protect you from infection.

Ssbaum
Ssbaum
20 days ago

Does anyone have advice on how to wash the hands of a 1 year old or how to wash your own hands while carrying a baby? I know handwashing is important but I feel like it’s the one thing I can’t figure out how to do one handed. I’m thinking in particular about how to do this in public places where putting baby down isn’t a good or possible option.

CourtneyR
CourtneyR
20 days ago

So interesting! Can you share a bit on the efficacy of hand sanitizer, using sanitizing hand wipes, or hand washing without soap as alternatives to hand washing? Thank you!

kate9
20 days ago
Reply to  CourtneyR
20 days ago

Alcohol based sanitizers are great because they work faster than plain soap so they are more likely to be used correctly and can be gentler on your skin than harsh scrubbing if paired with a good moisturizer. But they do not work well on norovirus. TBH, if you have norovirus in your house, you might as well go nuclear and drown everything in bleach because death is a better fate.

Baby bottles are drying on a towel after being washed.

Oct 18 2022

2 min read

Do I Need to Follow CDC Bottle Washing Guidelines?

CDC bottle washing recs: They are unrealistic, right? What am I risking by not following them? —Anonymous For reference, here Read more

Emily Oster
Close-up of HFMD blisters on a child's feet.

Jul 31 2023

8 min read

Everything You Need to Know About Hand, Foot, and Mouth

I am sometimes asked what I am hoping to achieve with ParentData. The answer is very simple. For me, so Read more

Emily Oster
A small child smiles and holds up bubble-covered hands while washing their hands.

Oct 11 2023

3 min read

How Often Should I Make My Kids Wash Their Hands?

When is it most important to wash your hands? My kindergarteners are getting frustrated by my insisting they wash their Read more

Emily Oster
Alt text

Dec 18 2023

7 min read

Is General Anesthesia Safe for Kids?

Some of the most complicated and agonized questions I get from parents of very young children are about the safety Read more

Emily Oster

Instagram

left right
SLEEP DATA 💤 PART 2: Let’s talk about naps. Comment “Link” for an article on what we learned about daytime sleep!

The first three months of life are a chaotic combination of irregular napping, many naps, and a few brave or lucky souls who appear to have already arrived at a two-to-three nap schedule. Over the next few months, the naps consolidate to three and then to two. By the 10-to-12-month period, a very large share of kids are napping a consistent two naps per day. Over the period between 12 and 18 months, this shifts toward one nap. And then sometime in the range of 3 to 5 years, naps are dropped. What I think is perhaps most useful about this graph is it gives a lot of color to the average napping ages that we often hear. 

Note: Survey data came from the ParentData audience and users of the Nanit sleep monitor system. Both audiences skew higher-education and higher-income than the average, and mostly have younger children. The final sample is 14,919 children. For more insights on our respondents, read the full article.

SLEEP DATA 💤 PART 2: Let’s talk about naps. Comment “Link” for an article on what we learned about daytime sleep!

The first three months of life are a chaotic combination of irregular napping, many naps, and a few brave or lucky souls who appear to have already arrived at a two-to-three nap schedule. Over the next few months, the naps consolidate to three and then to two. By the 10-to-12-month period, a very large share of kids are napping a consistent two naps per day. Over the period between 12 and 18 months, this shifts toward one nap. And then sometime in the range of 3 to 5 years, naps are dropped. What I think is perhaps most useful about this graph is it gives a lot of color to the average napping ages that we often hear.

Note: Survey data came from the ParentData audience and users of the Nanit sleep monitor system. Both audiences skew higher-education and higher-income than the average, and mostly have younger children. The final sample is 14,919 children. For more insights on our respondents, read the full article.
...

Happy Father’s Day to the Fathers and Father figures in our ParentData community! 

Tag a Dad who this holiday may be tricky for. We’re sending you love. 💛

Happy Father’s Day to the Fathers and Father figures in our ParentData community!

Tag a Dad who this holiday may be tricky for. We’re sending you love. 💛
...

“Whilst googling things like ‘new dad sad’ and ‘why am I crying new dad,’ I came across an article written by a doctor who had trouble connecting with his second child. I read the symptoms and felt an odd sense of relief.” Today we’re bringing back an essay by Kevin Maguire of @newfatherhood about his experience with paternal postpartum depression. We need to demystify these issues in order to change things for the better. Comment “Link” for a DM to read his full essay.

#parentdata #postpartum #postpartumdepression #paternalmentalhealth #newparents #emilyoster

“Whilst googling things like ‘new dad sad’ and ‘why am I crying new dad,’ I came across an article written by a doctor who had trouble connecting with his second child. I read the symptoms and felt an odd sense of relief.” Today we’re bringing back an essay by Kevin Maguire of @newfatherhood about his experience with paternal postpartum depression. We need to demystify these issues in order to change things for the better. Comment “Link” for a DM to read his full essay.

#parentdata #postpartum #postpartumdepression #paternalmentalhealth #newparents #emilyoster
...

What does the data say about children who look more like one parent? Do they also inherit more character traits and mannerisms from that parent? Let’s talk about it 🔎

#emilyoster #parentdata #parentingcommunity #lookslikedaddy #lookslikemommy

What does the data say about children who look more like one parent? Do they also inherit more character traits and mannerisms from that parent? Let’s talk about it 🔎

#emilyoster #parentdata #parentingcommunity #lookslikedaddy #lookslikemommy
...

SLEEP DATA 💤 We asked you all about your kids’ sleep—and got nearly 15,000 survey responses to better understand kids’ sleep patterns. Comment “Link” for an article that breaks down our findings!

This graph shows sleeping location by age. You’ll notice that for the first three months, most kids are in their own sleeping location in a parent’s room. Then, over the first year, this switches toward their own room. As kids age, sharing a room with a sibling becomes more common. 

Head to the newsletter for more and stay tuned for part two next week on naps! 🌙

#parentdata #emilyoster #childsleep #babysleep #parentingcommunity

SLEEP DATA 💤 We asked you all about your kids’ sleep—and got nearly 15,000 survey responses to better understand kids’ sleep patterns. Comment “Link” for an article that breaks down our findings!

This graph shows sleeping location by age. You’ll notice that for the first three months, most kids are in their own sleeping location in a parent’s room. Then, over the first year, this switches toward their own room. As kids age, sharing a room with a sibling becomes more common.

Head to the newsletter for more and stay tuned for part two next week on naps! 🌙

#parentdata #emilyoster #childsleep #babysleep #parentingcommunity
...

Weekends are good for extra cups of ☕️ and listening to podcasts. I asked our team how they pod—most people said on walks or during chores. What about you?

Comment “Link” to subscribe to ParentData with Emily Oster, joined by some excellent guests.

#parentdata #parentdatapodcast #parentingpodcast #parentingtips #emilyoster

Weekends are good for extra cups of ☕️ and listening to podcasts. I asked our team how they pod—most people said on walks or during chores. What about you?

Comment “Link” to subscribe to ParentData with Emily Oster, joined by some excellent guests.

#parentdata #parentdatapodcast #parentingpodcast #parentingtips #emilyoster
...

Humility. That’s why. That’s the whole reason.

#emilyoster #secondbaby #parentingjokes #parentinghumor

Humility. That’s why. That’s the whole reason.

#emilyoster #secondbaby #parentingjokes #parentinghumor
...

Bug season is upon us. Besides annoyance, this can bring up safety concerns, particularly with ticks. They are carriers of diseases, most notably Lyme disease. So what’s the best course of action?

Prevention is key! I suggest:
⭐ Regular tick checks
⭐ Using bug sprays with DEET 
⭐ Wearing long sleeves and pants in the woods

Some parents worry about DEET, but repellants with up to 30% DEET are recommended by both the CDC and AAP. The data says you’re in the clear, so go for it. Enjoy your summer!

#parentdata #emilyoster #tickseason #bugbites #bugspray

Bug season is upon us. Besides annoyance, this can bring up safety concerns, particularly with ticks. They are carriers of diseases, most notably Lyme disease. So what’s the best course of action?

Prevention is key! I suggest:
⭐ Regular tick checks
⭐ Using bug sprays with DEET
⭐ Wearing long sleeves and pants in the woods

Some parents worry about DEET, but repellants with up to 30% DEET are recommended by both the CDC and AAP. The data says you’re in the clear, so go for it. Enjoy your summer!

#parentdata #emilyoster #tickseason #bugbites #bugspray
...

The list of what not to do while pregnant feels longer than a CVS receipt. At ParentData, we want to empower you to make the right decisions for you. 

What an amazing group of women, and an honor to speak at the #MomsFirstSummit debunking parenting myths. 

What are some pregnancy rules you chose to bend after being empowered by data?

#emilyoster #parentdata #pregnancyproblems #pregnancymyths

The list of what not to do while pregnant feels longer than a CVS receipt. At ParentData, we want to empower you to make the right decisions for you.

What an amazing group of women, and an honor to speak at the #MomsFirstSummit debunking parenting myths.

What are some pregnancy rules you chose to bend after being empowered by data?

#emilyoster #parentdata #pregnancyproblems #pregnancymyths
...

Looking for Memorial Day Weekend plans? Might be the perfect time to give potty training a shot. Potty training is notoriously difficult, and we unfortunately don’t have a lot of evidence-based guidance on what works best. So I asked the ParentData community to fill out a survey and share their knowledge — about 6,000 people responded.

👉Comment “Link” for a DM to an article that summarizes all of the best potty training advice we collected. 

Remember, you are not alone in the potty training struggle! It can be incredibly challenging, so please give yourself some grace.

#emilyoster #parentdata #pottytraining #pottytrainingtips #toddlertips

Looking for Memorial Day Weekend plans? Might be the perfect time to give potty training a shot. Potty training is notoriously difficult, and we unfortunately don’t have a lot of evidence-based guidance on what works best. So I asked the ParentData community to fill out a survey and share their knowledge — about 6,000 people responded.

👉Comment “Link” for a DM to an article that summarizes all of the best potty training advice we collected.

Remember, you are not alone in the potty training struggle! It can be incredibly challenging, so please give yourself some grace.

#emilyoster #parentdata #pottytraining #pottytrainingtips #toddlertips
...

We’re hiring an Associate Editor at ParentData! More details at my link in bio. Please share with the great writers and data-loving people in your network. 📊💻

We’re hiring an Associate Editor at ParentData! More details at my link in bio. Please share with the great writers and data-loving people in your network. 📊💻 ...

Do you brand things a certain way to get your kid to accept it? Like calling carrots “rabbit popsicles”? Or telling them to put on their “super speed socks” in the morning? Share your rebrands in the comments below! You never know who you might be helping out 👇

#emilyoster #funnytweets #relatabletweets #parentingjokes #kidssaythedarndestthings

Do you brand things a certain way to get your kid to accept it? Like calling carrots “rabbit popsicles”? Or telling them to put on their “super speed socks” in the morning? Share your rebrands in the comments below! You never know who you might be helping out 👇

#emilyoster #funnytweets #relatabletweets #parentingjokes #kidssaythedarndestthings
...

Have you ever panic-googled a parenting question when everyone else is asleep? If so, you’re not alone. 

Today is the first episode of a new biweekly series on my podcast: Late-Night Panic Google. On these mini-episodes, you’ll hear from some familiar names about the questions keeping them up at night, and how data can help. First up: @claireholt!

Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#parentdata #emilyoster #claireholt #parentingstruggles #parentingtips #latenightpanicgoogle

Have you ever panic-googled a parenting question when everyone else is asleep? If so, you’re not alone.

Today is the first episode of a new biweekly series on my podcast: Late-Night Panic Google. On these mini-episodes, you’ll hear from some familiar names about the questions keeping them up at night, and how data can help. First up: @claireholt!

Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#parentdata #emilyoster #claireholt #parentingstruggles #parentingtips #latenightpanicgoogle
...

Sun safety is a must for all ages, especially babies! Here are my tips for keeping your littlest ones protected in the sunshine:
☀️ Most importantly, limit their time out in hot weather. (They get hotter than you do!)
☀️ Keep them in the shade as much as possible when you’re out.
☀️ Long-sleeve but lightweight clothing is your friend, especially on the beach, where even in the shade you can get sunlight reflecting off different surfaces.
☀️ If you want to add a little sunscreen on their hands and feet? Go for it! But be mindful as baby skin tends to more prone to irritation.

Comment “Link” for a DM to an article on the data around sun and heat exposure for babies.

#sunsafety #babysunscreen #babyhealth #parentdata #emilyoster

Sun safety is a must for all ages, especially babies! Here are my tips for keeping your littlest ones protected in the sunshine:
☀️ Most importantly, limit their time out in hot weather. (They get hotter than you do!)
☀️ Keep them in the shade as much as possible when you’re out.
☀️ Long-sleeve but lightweight clothing is your friend, especially on the beach, where even in the shade you can get sunlight reflecting off different surfaces.
☀️ If you want to add a little sunscreen on their hands and feet? Go for it! But be mindful as baby skin tends to more prone to irritation.

Comment “Link” for a DM to an article on the data around sun and heat exposure for babies.

#sunsafety #babysunscreen #babyhealth #parentdata #emilyoster
...