Does Hand Sanitizer Actually Work? A Disgusting Science Experiment

Before coronavirus, the last time I used hand sanitizer was probably a few years ago at some music festival port-a-pottie. Now, “phone, keys, wallet” has become “phone, keys, wallet, mask, hand sanitizer.” Using it is now so ingrained in me that I absentmindedly use it anytime I touch anything in public.

I have no idea if it works, but I assume it does! We are told that Purell “kills 99.9 percent of disease-causing germs,” but I really have no way of analyzing whether or not that is true. Or, at least, I thought I didn’t, until I remembered that it is very easy to grow bacteria and that, the last time I did so, everyone seemed to like it a lot.

I’d like to preface this entire post by saying that I am a journalist, not a scientist, and that this isn’t anything close to a real scientific study. Many studies have shown that, generally speaking, hand sanitizer works, and you should use it regardless of what I ultimately found (really, you should wash your hands with soap and water, which is more effective, but hand sanitizer is good if you can’t.) Also, I didn't have access to a clean room during the pandemic, and so it is possible and maybe even likely that for the brief moments my petri dishes were exposed to the air of my apartment they became contaminated. I took precautions to prevent this, such as using individually-wrapped sterile cotton swabs and opening up the petri dishes only to pour agar and swab them; they were exposed to air for only a few seconds.

Regardless, there was some joy in seeing for myself the before-and-after of using hand sanitizer through the magic that is bacterial cultures and colonies.

SARS-Cov-2 is a virus, not bacteria, and viruses do not replicate in agar petri dishes. But I have barely left my house in seven weeks, have had nothing to do, and learned that homesciencetools.com’s $15.95 “Bacteria Hand Washing Experiment Kit” is a best-selling experiment that can be safely conducted by anyone who is bored and over the age of 10.

“It's often said that one of the most effective ways to prevent the spread of illness is washing hands with soap and water—is this really true?,” the website asks. “Use this complete bacteria project kit to find out,” it implored me.

And so, on one of the first days of lockdown, I ordered the kit and set up the experiment when it arrived a few days later.

Most importantly, I wanted to make and test DIY hand sanitizer to figure out whether or not it actually works. I have no reason to believe that it doesn’t, given that the World Health Organization has recipes, which I followed, that are used all over the world. But lots of people are making their own hand sanitizer these days because it is sold out everywhere. Even its main component, rubbing alcohol, is sold out at all the stores near me.

Thankfully, I had a bottle of 70 percent isopropyl alcohol on hand already for cleaning electronic components in old MacBooks I wanted to repair once upon a time, but that’s another story. I poured some into a spray bottle and added a few drops of hydrogen peroxide. Luckily for me, this rubbing alcohol already had glycerin in it, which the WHO says is used as a “humectant,” to "improve acceptability of the product," which after a lot of Googling I learned means “something that makes your skin feel less dry.” If you do not have glycerol you can just not use it; the alcohol is the stuff that kills germs and if you didn’t notice we’re in a pandemic so don't let the perfect be the enemy of the good enough.

It is exceptionally easy to make your own hand sanitizer, so easy that you really don’t need an article to explain to you what to do. Basically all you need to do is make sure that your alcohol concentration is high enough to kill microbes; the WHO’s recipe ends up with a mixture that is 75 percent alcohol. A lot of popular hand sanitizers are 62 percent alcohol, which seems to be about the lowest you can get away with. So, put some alcohol in a spray bottle and you’ve “made” hand sanitizer.

When I designed this experiment in my head, I had planned on pitting DIY hand sanitizer against Purell to see if there is actually any sort of difference. But I have not seen an honest-to-god bottle of Purell in a store in more than two months, and so the “real” hand sanitizer I used to start the experiment was this bottle that I will call “watermelon brand” hand sanitizer that my girlfriend had in her purse. For a long while was the only hand sanitizer we had.

We recently ran out of watermelon brand hand sanitizer, but in the meantime we have secured a worthy replacement. Our new “real” hand sanitizer that has since replaced it, and which I use after doing very brave, death-defying things like touching a touch screen at the grocery store, is called “Thanks for Holding My Hair Back hand sanitizer.” It is made by a novelty brand called BlueQ that sells socks and oven mitts with jokes on them. The label has a picture of a person puking and her friend holding her hair back. Though these girls are children, its name presumably refers to people who puke after attending a party, back when we used to have parties before all the unpleasantness. This novelty hand sanitizer was mailed to me by my mom to keep me safe during the pandemic around the time when semi trucks pulled up outside of hospitals around the corner from my house to store the bodies of people who died from coronavirus. According to the bottle, it contains 62 percent ethyl alcohol and expired in January 2016, which is something I realized five seconds ago. BlueQ is currently sold out of hand sanitizer, if you're wondering.

ANYWAY, as per the instructions on my bacteria growing kit for third graders, I heated up my agar in the microwave and poured it out into several petri dishes, then let them cool and set. I then did a series of swabs using sterilized cotton swabs and waited to see what grew, which takes about 10 days. I left the petri dishes in a box in my closet next to my jeans that I have not worn in two months.

As with the last time I cultured bacteria, I have no idea what I grew nor if any of it is harmful, but a lot of it sure looks gross! Because this science experiment was marketed to children, you should treat my findings more or less the same as you would treat a writeup from an elementary schooler, if they still went to school. Ultimately I did not test handwashing with soap and water because I am not made of petri dishes.

Here are pictures of what I grew and some brief thoughts:

Control (right hand):

I swabbed my right hand after not having washed or sanitized my hands for a few hours in and around my house.

Watermelon sanitizer (right hand):

I used watermelon brand sanitizer on my right hand only. A large spore of… microbes grew.

Control (left hand):

I swabbed my left hand after not having washed or sanitized my hands for a few hours in and around my house. This is definitely the grossest one, with various molds and colorful bacteria growing.

DIY Hand sanitizer (left hand):

I used my DIY hand sanitizer on my left hand. Lots of little colonies of bacteria grew, but in my uneducated opinion these do not seem particularly gross.

How dirty are doorknobs?:

I re-sanitized my right hand with DIY hand sanitizer, then opened my front door, then immediately swabbed it to see if bacteria would get on my hands from merely touching a door for a couple seconds. To my surprise and disgust, a lot of things grew! Perhaps doorknobs should be made of copper.

Phone (Dirty):

Swabbed my iPhone, before cleaning it. A throwback to simpler times.

Phone (Cleaned with Pledge wipe):

My mom also sent me a package of Pledge wipes. This was a great development because we ran out of Clorox wipes comically early during the pandemic. We have maybe six Pledge wipes left, and I used one on this dumb experiment. I wiped my phone, then swabbed it. Pledge wipes appear to be an unimpeachable product (the bump you are seeing here is agar buildup).

I definitely grew less bacteria after using hand sanitizer than I did when I swabbed my dirty hands, which is good. But hand sanitizer is not perfect, which is backed up both by my imperfect study as well as various peer reviewed studies. In fact, GOJO, the maker of Purell, is currently being sued for what plaintiffs say are misleading claims about the efficacy of its product.

My DIY hand sanitizer seemed to work quite well, assuming the few microbes I grew are not dangerous. But bacteria or some sort of visible microbe grew on every petri dish except for my phone post-Pledge wipe. This could have happened because perhaps I didn’t use the hand sanitizer thoroughly enough, or perhaps my petri dishes got contaminated somehow. Or maybe the hand sanitizer simply didn’t kill everything. According to the CDC, “Alcohol-based hand sanitizers can quickly reduce the number of microbes on hands in some situations, but sanitizers do not eliminate all types of germs.” The CDC says you should use a lot of hand sanitizer and let it dry completely before wiping it off.

The takeaway is that science is fun and that germs are everywhere. The real concern right now is not a bacteria but a coronavirus, which I knew coming into this that I would be unable to detect (I anxiously await Home Science Tools' upcoming Coronavirus Education Kit, $39.99). Experts say that hand sanitizer is better than nothing if you can't wash your hands. I'd suggest you keep using it when you touch things, but mainly remember to wash your hands, don't touch your face, and never, ever touch a doorknob.