Together with wearing a mask and maintaining social distancing, keeping your hands clean is essential for preventing the spread of the coronavirus (COVID-19). The CDC and other health agencies recommend washing hands with soap and water whenever possible, scrubbing all surfaces of the hands – including the back of the hands, between the fingers, and under the nails – for at least 20 seconds. But there are times when soap and water are not available. In those cases, hand sanitizers – when used correctly – can be just as effective at killing COVID-19 and other types of viruses.
A brief history of the importance of clean hands
Nowadays, handwashing might seem as self-evident as wearing a seatbelt or washing our teeth, but hand hygiene hasn’t always been a given. Religious handwashing rituals have been around for thousands of years; Judaism, Sikhism, and Islam, for example, all outline precise handwashing rules in their holy texts. In the Catholic religion, some priests still practice sprinkling their hands with holy water before the consecration of bread and wine. But it wasn’t until about 130 years ago that the life-saving powers of clean hands were discovered.
In the 1840s, a Hungarian obstetrician named Ignaz Semmelweis became worried at the difference between maternal death rates in two clinics at the Vienna General Hospital. The two clinics were located at the same hospital and used almost the same practices and techniques. But, for some reason, mortality rates were much higher at one of the clinics. The only difference between the locations was their staff: one clinic was run by doctors, and the other was led by midwives.
At the time, it was thought that miasma, or “bad air,” was responsible for spreading disease. These poisonous vapors were believed to emerge from rotting corpses and other types of decomposing matter. But that didn’t explain the disparities between maternal deaths. So, after testing several failed hypotheses, a revelation came to Semmelweis in 1847 when one of his colleagues cut his hand with a scalpel during an autopsy. Soon after, the doctor died exhibiting the same symptoms as the mothers that passed at the clinic.
Because the concept of handwashing didn’t exist at the time, doctors performed all kinds of medical procedures without washing their hands. That meant that it was normal for physicians to perform an autopsy on a corpse and deliver a baby right after.
That realization led Semmelweis to theorize that miasma from the corpses was perhaps clinging to the doctor’s hands and then infecting mothers during childbirth. On the other hand, midwives – who didn’t wash their hands either – were solely attending births, so they didn’t have the same kind of cross-contamination issues. To test his hypothesis, Semmelweis ordered doctors to clean their hands and tools with a chlorine solution.
The experiment was a success – clean hands instantly started saving lives. Although Semmelweis wrongly believed that childbed fever was coming directly from corpses, and not from germs as it was later discovered, mortality rates at the delivery room dropped significantly. Unfortunately, the idea of personal hygiene was received with great resistance in part because Victorians found the idea of their hands being dirty insulting. Soon after his experiments, Semmelweis’ ideas were dismissed, and he was committed to a mental institution, where he died at the age of 47.
How do hand sanitizers work?
Over the decades following Semmelweis’ discovery, a deeper understanding of germs emerged, and attitudes towards hygiene slowly shifted. Today, we know that there are millions of microbes – viruses, bacteria, fungi – capable of causing disease. These bugs live in all kinds of environments, including surfaces such as doorknobs, countertops, handrails, etc., but they can’t move on their own, so they depend on living things to spread them around.
Common germs such as the influenza virus, and more recently COVID-19, lie in wait on surfaces – including other people’s hands – until they can hitch a ride from another host. They enter the body when our hands come in contact with porous membranes such as the mouth, eyes, and nose. We then transmit these germs ourselves by touching our noses, eyes, or mouths and then touching other surfaces or by coughing and sneezing.
Because our hands are the main driving germs inside our bodies, cleaning them frequently is a sure-fire way of preventing the spread of many types of infections. Washing them with soap and water is generally the best way of killing germs, but when they are not readily available, hand sanitizer can also help avoid getting sick and spreading bugs around.
The main – and most important – ingredient in hand sanitizer is alcohol. Alcohol is used in hand sanitizers for its ability to quickly kill disease-causing microbes by dissolving the outer fatty membrane of viruses and bacteria and destroying their inner structure – similar to what happens when you wash your hands with soap and water.
Most hand sanitizers are made with isopropanol or ethanol, two types of alcohol highly soluble in water. Generally speaking, both are highly effective at killing certain types of viruses and bacteria. However, ethanol – the chemical present in alcoholic drinks – is slightly more potent than isopropanol (aka rubbing alcohol).
Hand sanitizers are typically marketed as capable of destroying “99.9 percent of germs,” which is certainly true under some circumstances. The effectiveness of hand sanitizer depends on three things: the alcohol concentration in the formula, the type of germ, and how dirty or oily your hands actually are.
Alcohol concentration: not all hand sanitizers are alcohol-based, and not all alcohol-based hand sanitizers contain the appropriate amount of alcohol needed to kill germs. That means that not all kinds of hand sanitizers are effective against SARS-CoV-2, the virus that causes COVID-19.
According to a systematic review of studies published in The Journal of Hospital Infection, ethanol is very effective at enveloping and inactivating certain viruses within 30 seconds at a concentration of 80 percent. Lower concentrations, such as under 60 percent, might take longer to neutralize the virus – maybe a minute or more. By which time, however, the alcohol may evaporate from the skin before it can destroy the germs. To prevent the spread of COVID-19, the CDC recommends using a sanitizer that contains at least 60 percent ethanol or 70 percent isopropanol when soap and water are not available.
Types of germs: at the appropriate concentration, alcohol-based hand sanitizers can eliminate a broad range of pathogens, including viruses, bacteria, and fungi. However, alcohol is not effective at neutralizing all bugs. Research suggests that alcoholic preparations cannot destroy the virus that causes hepatitis A. It is also ineffective against the poliovirus – the virus that causes poliomyelitis.
Soiled hands: hand sanitizers may not work well when hands are visibly soiled or too greasy.
Does alcohol-free hand sanitizer protect against COVID-19?
The short answer is no. Alcohol-free hand sanitizers have been popping up all over the internet and grocery stores during the COVID-19 outbreak. These sanitizers are typically made with a disinfectant chemical called benzalkonium chloride, essential oils, and other ingredients that aren’t capable of killing coronaviruses.
Shortages of hand sanitizer caused by this public health emergency have also led some to make their own hand sanitizer solutions at home, but there are several downsides to this. First of all, some ingredients might not be effective at killing the pathogens that cause COVID-19, leaving you unprotected without your knowledge.
Additionally, rubbing alcohol is not enough to make hand sanitizer, and most people don’t have the right ingredients and tools at home. Non-sterile working environments might contaminate the mixture. The Food and Drug Administration (FDA) has also received reports of skin burns from DIY hand sanitizers.
New FDA guidelines
Now that hand sanitizer is part of our day to day existence, knowing whether the product you are applying so frequently to your hands is safe or not is more important than ever. In June, the FDA issued a warning against nine tainted hand sanitizer brans made by Eskbiochem. The agency has recently expanded its list, and it now contains over 75 hand sanitizers for containing dangerous methanol levels.
Methanol, also called wood alcohol, is a toxic substance that can cause nausea, nerve damage, and blindness when absorbed through the skin. Ingesting methanol can be lethal. According to experts, young children are at the highest risk of methanol poisoning.
The FDA recommends consumers to avoid purchasing and using hand sanitizers that:
- Have been tested by FDA and found to contain methanol or 1-propanol
- Are labeled to contain methanol
- Have been tested and were found to have microbial contamination
- Are being recalled by the manufacturer or distributor
- Has less than the required amount of alcohol
- Are purportedly made at the same facility as products that have been tested by FDA and found to contain methanol or 1-propanol
- Are packaged in containers that resemble a food/beverage container, presenting an increased risk of accidental ingestion
Click here to see the FDA’s complete do-not-use / RECALL list.
Using hand sanitizer properly
One common mistake is using too little hand sanitizer because they tend to be too sticky or goopy. The World Health Organization recommends applying a “coin-sized” amount of sanitizer, enough to cover both sides of both hands and between the fingers.
Like washing your hands with soap and water, the process of applying hand sanitizer should take at least 20 seconds. It’s important to pay special attention to your thumbs, the back of the hands, and fingers. You should stop rubbing when the sanitizer has evaporated and your hands feel dry. Store your hand sanitizer in a cool, dry location away from sunlight and heat.
Hand sanitizer safety
While hand sanitizer is a great alternative when soap and water are not readily available, they are regulated by the FDA as over-the-counter (non-prescription) drugs and should be used with caution. Keep these tips in mind for using hand sanitizer safely:
- Never ingest hand sanitizer
- Store hand sanitizer out of reach of children and pets
- Children should only use hand sanitizer under adult supervision
- Hand sanitizer is flammable: keep away from heat and open flames
- Don’t touch your eyes, mouth, or nose immediately after using hand sanitizer
- Read the label and consult the FDA’s do-not-use list before purchasing a hand sanitizer
- If your hand sanitizer lists methanol as one of its ingredients, discontinue its use immediately
