The idea that hand sanitiser can blow up or cause a fire in vehicles has been something that’s been floating around for the last few months. But where exactly did it come from?

It all started with a few Facebook posts that gained momentum in May that showed images of damaged car doors – posts that have been re-shared thousands of times.

But in June, NHS bosses seem to also issue a warning about hand sanitiser in vehicles and the hot weather – effectively warning against storing hand sanitiser in hot vehicles. This seemed to add some weight to the claims circulating like wildfire on social media.

The connection between hand sanitiser and fires is mostly based on the fact that hand sanitiser has a fairly low temperature flash point. This means that once the product reaches a certain temperature, its starts to evaporate into the air - making the air extremely flammable.

The flash point temperature of hand sanitiser is on average around 21 degrees.

However, the key thing to bear in mind with this claim is that, even though hand sanitisers are potentially flammable, they cannot just ignite by themselves. There would need to be some sort of spark to start a fire.

The flammable ingredients in hand sanitiser would need to be at a lot higher temperatures for it to ignite by itself without a spark – temperatures of over 350 degrees.

The National Fire Chiefs Council confirmed this and that "hand sanitiser kept in cars do not pose a fire risk".

The fact checking organisation, Full Fact, also confirmed that hand sanitiser doesn’t just ignite by it self and it would need an external spark to cause a fire.

So, can hand sanitiser really blow up in your car?

It’s extremely unlikely, and definitely not just from leaving your hand sanitiser in the car on a warm day. There would have to be other factors involved to cause a spark, which would then potentially cause a fire.