Why you shouldn't leave hand sanitisers in your car - and not because it'll start a fire

While it is recommended to wash your hands regularly to protect yourself against the coronavirus, it is not possible when you are travelling. Hence, many people have started to carry with them bottles of alcohol-based hand sanitisers for some relief.

But where do you store your sanitisers? Some people have placed sanitisers in their cars for accessibility, but is it safe?

Here are some reasons why experts have warned people that they should not leave their hand sanitisers in the car, at least not for a long period of time. But are all the reasons valid?

Let's find out!

1. It may lose its effectiveness

Florida Gold Coast University Associate Professor Dr Greg Boyce warns that leaving a hand sanitiser in the car for a long period of time at high temperatures can cause it to lose some efficacy, as the active ingredient could evaporate.

As alcohol is the active ingredient that kills bacteria and viruses, it needs to be present at a certain concentration for the greatest effectiveness.

Hence, "you want it above 60 per cent so if it stayed out for quite a while you would rather not use it", Greg said.

But how does the alcohol evaporate if the bottle is closed?

According to Healthline, although hand sanitiser bottles protect the alcohol from being exposed to the air when not in use, evaporation is still possible as the containers may not be airtight.

This is also why sanitisers have an expiration date as the manufacturer estimates the amount of time needed for the active ingredient to drop to a less effective percentage.

With warmer temperatures, the evaporation process is sped up and thus it may lose its effectiveness quicker.

2. Warm sanitisers can irritate the skin

Malaysian pharmaceutical company Argania.my advises against leaving hand sanitisers in hot vehicles as warm sanitisers may irritate the skin. The company advised that the liquid should be left to cool first before use.

While we have yet to find conclusive evidence on whether heat is a factor, what we do know is frequent use of sanitisers may lead to irritation on the skin.

Dermatologist Lynn Chiam from Children and Adults Skin Hair Laser Clinic told Today that certain ingredients in sanitisers can strip away the skin's natural oils, which act as a barrier to protect the skin.

"With a defective barrier function and cracks, tears in the skin from dryness, bacteria and viruses can enter the skin more readily", said Lynn.

3. If leaked, sanitisers can damage your car's interior

A research conducted by Ford engineers found that the ingredients in sanitisers can cause the interior surfaces of the car to wear prematurely.

In their experiment of testing cars at high temperatures in Turkey, they discovered "high wear" on cars and the cause was traced to ethanol, a common alcohol used in sanitisers.

Automotive site WapCar.my has also explained how cleaning the car with alcohol can speed up the wear and tear process as the alcohol dries up leather and vinyl while removing its protective lacquer.

4. Sanitisers are flammable, but are unlikely to start car fires

Singapore's Health Sciences Authority (HSA) has advised the public to be careful on how they store their alcohol-based hand sanitisers.

According to HSA, alcohol-based sanitisers are generally flammable, more so if they have a high concentration of alcohol. They should therefore be kept in cool areas and not exposed to heat.

In April this year, a mother in the UK claimed that a hand sanitiser had "exploded" after leaving it in a car for four weeks under the sun.

She warned of the dangers of leaving a hand sanitiser in a hot car after her 11-year-old daughter was injured in the eye by the "exploding" bottle when she opened it.

While there was evident damage to her eye, ophthalmologists could not confirm if it was due to the product itself or the force with which it hit her eye.

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However, claims that sanitisers can cause car fires have been debunked by AFP Thailand's fact-check. A circulated video on the internet, which showed two men getting into a car that quickly caught on fire purportedly caused by a hand sanitiser was found to be a hoax.

Brazilian fact-checkers Aos Fatos and Estadão Verifica also found that a car would need to reach a temperature above 300 degrees Celsius for hand sanitisers to catch fire. Even so, the hand sanitiser has to be present in large amounts, as explained in a video by the National Fire Protection Association. And by large amounts, it refers to an estimate of five gallons.

So the conclusion is that while the magnification of light through a bottle of hand sanitiser or from the close proximity of an open flame can technically start a fire, the likelihood of your hand sanitiser combusting is still pretty low.

To leave or not to leave hand sanitisers in your car

From what we have researched, if you're just stepping out of the car on a short trip to the grocery store, it may be fine, but perhaps not for a longer period of time.

We'd recommend storing your hand sanitiser in a cooler area of the car if possible or bring it around with you in your bag when you leave your car.

ALSO READ: Placing a water bottle in your car can be deadly. Here's why

trining@asiaone.com