Hand sanitizer poses a risk in a hot car — here’s how to stay safe

Hand sanitizer has become liquid gold since COVID-19 landed in America, sparking shortages across the country. While the product is slowly making its way back on shelves and online retailers, people who have it want to treat their sanitizer like the precious commodity it is.

But, now that the weather is warming up, there’s a new question to consider: Is it safe to keep hand sanitizer in the car? Will hot temperatures somehow render hand sanitizer ineffective? And can leaving your hand sanitizer out actually cause a fire in your car, or is that a myth?

Before you panic about the fact that your hand sanitizer is a permanent fixture in your car, know this: It’s probably OK to keep on doing this—if you take the right precautions. Here’s what you need to know about keeping hand sanitizer in your car.

First, it’s important to understand the basics of hand sanitizer. There are different forms of hand sanitizer, but the most common type — and the one that’s been found to kill SARS-CoV-2, the virus that causes COVID-19 — is made with at least 60 percent alcohol, per the Centers for Disease Control and Prevention (CDC). “The active ingredient in there is alcohol, but it’s in an emulsion that stabilizes it,” say Dr. William Schaffner, an infectious disease specialist and professor at the Vanderbilt University School of Medicine. That emulsion can be a slew of different things, but it’s often a moisturizing ingredient, like aloe vera, Schaffner says.

So, is it OK to keep hand sanitizer in your car?

The big concern with this is heat. “Hand sanitizer is dependent on the amount of ethanol content,” states Jamie Alan, an assistant professor of pharmacology and toxicology at Michigan State University.“If enough ethanol [a form of alcohol] evaporates out, then it could drop the concentration to one that is ineffective,” she says. But it can be a little more complicated than that. An older study published in the Journal of the American Dietetic Association analyzed six recipes that included alcohol and found that it actually takes some time to fully cook out alcohol — as many as three hours. After food was exposed to normal cooking temperatures for 15 minutes, about 40 percent of the alcohol content remained. After an hour, it went down to 25 percent, and things progressed from there.

It seems, then, like keeping your hand sanitizer in the car has the potential to render it ineffective, but Schaffner says it’s not necessarily the case. Your car would likely need to get really hot to burn off the alcohol content in your hand sanitizer, he says. A study published in the journal Temperature found that a car parked in the sun on a day where the outside temperature was 95 degrees developed an internal temperature of 116 degrees within an hour. The dashboard got as hot as 157 degrees.  Alcohol boils at around 173 degrees Fahrenheit, so the odds of your hand sanitizer reaching that level are somewhat low, Alan says. But, if you live in an especially hot area, it’s not impossible. If your hand sanitizer did reach that temperature, though, Schaffner says you’d know it: Your sanitizer would look different or the cap would pop off from the built-up pressure and cause a mess.

Some people are also concerned with the sanitizer being exposed to light, and that’s actually a valid concern. Leaving hand sanitizer in a hot car in direct sunlight can actually lead to a fire, says Dr. Amesh A. Adalja, senior scholar at the Johns Hopkins Center for Health Security.  “Most hand sanitizer is alcohol-based and a flammable substance,” he says. “You want to make sure it’s not too hot in your car.”  The National Fire Protection Association (NFPA) released a video warning about this earlier this year, and Wisconsin’s Western Lakes Fire District recently shared a photo on Facebook that went viral of a car with a driver’s side door that was torched from a hand sanitizer fire.“You just want to store your hand sanitizer safely so it doesn’t catch on fire and melt in your car,” Adalja says.

In a perfect world, your hand sanitizer would be stored in a cool, dry place. In reality, you’re probably still going to want to keep it in your car. So, to play it safe, store your hand sanitizer out of the sunlight. “I keep mine in my glove compartment,” Schaffner says.  If you want to have it handy at all times, Schaffner says it’s also a good idea to carry your sanitizer in your purse or backpack instead of your car. Also, keep tabs on your hand sanitizer’s expiration date. Yes, it does expire. “The FDA does not have data for stability and effectiveness past the expiration date, so it may or may not be good after that,” Alan says. “Probably if it’s relatively close to the expiration date, it’s OK but that’s really hard to say.”

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Photo Credit:  zuzana caprnkova / Shutterstock.com