Hand sanitizer has been flying off the shelves since the start of the COVID-19 pandemic. This demand left stores all over the country out of stock, and counterfeit products that might have adverse health effects have also entered the market. And there have already been multiple recalls of products—either for being counterfeit versions of the real thing, not being authorized for sale in Canada or for having potentially harmful ingredients. Health Canada has a comprehensive list of all its authorized hand sanitizers and disinfectants currently on the market to help Canadians make informed purchases and avoid counterfeit products.

One important thing to watch out for if you’re shopping: Health Canada has approved both alcohol based and non-alcoholic hand sanitizers. However, it’s been reported that non-alcoholic hand sanitizers are potentially less effective in preventing the spread of COVID-19.

Here is everything you need to know about hand sanitizers, their effectiveness and what to look out for when you’re shopping.

Why aren’t non-alcoholic hand sanitizers as effective against COVID-19?

Alcohol makes viruses non-infectious by drying them out. “By removing the water from the virus particles, it disrupts the structure of the proteins on the surface of this virus, including here the spike protein, and renders the virus non-infectious,” explains Dasantila Golemi-Kotra, an associate professor of microbiology at York University in Toronto. “Ethanol works quite well because it can remove the water and dries the particle to a point where it’s not infectious.” Non-alcoholic hand sanitizers don’t disrupt the structure of the virus as effectively.

In a pinch, if you can’t wash your hands with soap and water (which is still the most effective way to clean them) or if you’re out of alcohol-based sanitizer, Golemi-Kotra says that a non-alcoholic hand sanitizer is better than nothing. Especially if you have wipes. “The mechanical rubbing of the wipes really removes the virus particles from the skin. It may not kill it, but you still clean yourself,” she says.

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Okay, so it sounds like I should definitely buy alcohol-based hand sanitizers. What percentage of alcohol does a hand sanitizer need to be to be effective against COVID-19?

The Centers for Disease Control and Prevention (CDC) recommends using hand sanitizers that have 60 to 95 percent alcohol. Golemi-Kotra agrees with this recommendation, remarking that that range seems to be the sweet spot in terms of the alcohol’s efficiency in killing the virus. “If you go lower than that, you won’t have enough ethanol to do the process of drying out the virus particles,” she says. “And sometimes the problem with having too much ethanol is that it evaporates very quickly before it can do its job.”

What other ingredients should consumers be looking for?

To make sure you’re buying hand sanitizer with alcohol, check the ingredients panel for ethanol, isopropyl alcohol or ethyl alcohol. Some common non-alcoholic active ingredients include benzalkonium chloride, triclosan and chlorhexidine gluconate.

Aside from alcohol content, consumers should also be looking for ingredients that shouldn’t be in the formula. One major one to look out for is methanol. Though it’s great at destroying the virus, it’s also toxic to human tissue cells. Health Canada recently issued a recall of hand sanitizers that contain methanol and noted that frequent use of methanol can lead to dermatitis, eye irritation, upper respiratory system irritation and headaches.

Acetaldehyde, a toxic byproduct of ethanol, is another component to watch out for. According to Golemi-Kotra, there was a shortage of food-grade and pharmaceutical-grade ethanol when the pandemic first started, so Health Canada approved the limited use of technical-grade ethanol (which is less pure and safe) for hand sanitizer manufacturing. Acetaldehyde naturally occurs in technical-grade ethanol and is potentially carcinogenic. Hand sanitizers that have acetaldehyde in them cannot be used by children or people who are pregnant or breastfeeding—and must be labelled.

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How should I store my hand sanitizer so it stays effective?

One place to avoid keeping hand sanitizer? Your hot car. Though reports of hand sanitizers exploding in hot cars have largely been dispelled, ethanol might escape the hand sanitizer bottle as vapour when it’s heated. This won’t cause an explosion, but the vapors might be flammable. This is more likely in a water-like formula, according to Golemi-Kotra. “It’s much easier for ethanol to evaporate [into vapour] with those kinds of compositions, but good thing nowadays most hand sanitizers have a more gel-like consistency,” she says. Another issue with these ethanol vapours is that it decreases the overall concentration of alcohol in the bottle—making it less effective.

Golemi-Kotra recommends keeping your hand sanitizer at room temperature to keep them stable and effective.

What does it mean when a hand sanitizer is approved for use by Health Canada?

The requirements for hand sanitizer approval in Canada can be found in their online Antiseptic Skin Cleansers monograph, which describes the requirements needed to be authorized for sale (such as a Drug Identification Number (DIN) or a Natural Product Number (NPN)). Products approved by Health Canada have gone through an application process which accesses the product’s safety, efficacy and quality. Only hand sanitizers approved by Health Canada can be sold in Canada. However, According to a spokesperson from Health Canada, no hand sanitizers have been approved with specific COVID-19 related claims. “Although they have not been tested for effectiveness against viruses such as coronaviruses, hand sanitizers can help reduce the risk of infection by—or spread of—microorganisms,” says the spokesperson.

Read this next: What Canadians Should Know Before Travelling During COVID-19

Got it! Now how do I use hand sanitizer the right way?

According to the CDC, apply hand sanitizer to the palm of your hand (check the product label first to see how much to use) and rub it all over the surface of your hands until they’re dry. Public Health Ontario recommends rubbing your hands for 15 seconds.

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