Some airlines spray insecticide in the cabin while passengers are still in their seats, and if you've never seen it, it can be a strange thing to watch. A flight attendant walks the aisle holding an aerosol can in each hand, the cabin fills with a faint mist, and an announcement asks you to stay seated. I've had it happen on flights from Mumbai to London, Jakarta to Kuala Lumpur and Guangzhou to Bangkok. Every time, half the cabin looked around wondering what had just happened.
What It Is
The practice is called disinsection, and its job is to kill any mosquitoes or other insects that hitched a ride on the plane before they can get out at the destination. Countries use it to keep out diseases spread by mosquitoes, like malaria, dengue, Zika and yellow fever, along with insects that could damage crops.
The spray usually contains d-phenothrin, an insecticide the World Health Organization recommends for this use. It attacks an insect's nervous system, which is why it works on mosquitoes at a dose that's tiny for a person.
Which Countries Require It
Not every country asks for the spray with people on board. According to the US Department of Transportation's list, these require it while passengers are in the cabin: Ecuador (for flights to and within the Galápagos), Grenada, Guyana, India, Kiribati, Madagascar, Panama, Seychelles, Tanzania, Timor-Leste, Trinidad and Tobago, Uruguay and Zimbabwe.
Explained
The Three Ways Airlines Spray for Insects
With you on board
Aerosol in the cabin
Crew walk the aisle with spray cans. Required by India, Panama, Tanzania, Zimbabwe, Seychelles, Madagascar and a handful of others.
Before you board
Long-lasting surface treatment
Cabin surfaces are treated while the plane is empty. An option in Australia, New Zealand, Fiji, Chile and a few others.
Only some flights
Selective
Usually flights from areas with mosquito-borne disease. Countries include France, Italy, the UK, South Africa, Thailand and Indonesia.
Country lists per the US Department of Transportation. Rules change, so check before you fly if you're sensitive.
Contrail
Other countries, including Australia and New Zealand, let airlines treat cabin surfaces with a longer-lasting insecticide while the plane is empty instead. A larger group, which includes France, Italy, the UK, South Africa, Thailand and Indonesia, only requires it on certain flights, usually ones arriving from places where mosquito-borne diseases are common. The rules change from time to time, so it's worth checking if you're sensitive and flying somewhere tropical.
Is It Safe?
The World Health Organization says aircraft disinsection doesn't present a risk to human health when it's done properly, though it notes that some people may feel temporary discomfort afterward. That's the official answer most airlines lean on.
The US takes a more cautious view. The Environmental Protection Agency has had a policy since 1996 of not registering any insecticide for use in aircraft cabins, saying the available data don't show that the benefits outweigh the risks. That's one reason you won't see the spray on flights within the US.
For most travelers, a few seconds of mist on the occasional flight is very unlikely to do you harm. People with asthma, allergies or chemical sensitivities may notice it more, with things like a scratchy throat, watery eyes or a headache.
How to Handle It
If the spray bothers you, there are a few easy things you can do:
- Cover your nose and mouth with a scarf or a mask while the crew walks through, and close your eyes for a moment.
- Keep anything you'll eat or drink covered until the mist settles.
- Tell a flight attendant before the spray if you have asthma or a sensitivity. They can't skip your row, but they can make sure you know when it's coming.
- If you know your route requires it, check with your doctor beforehand.
It's one of those parts of flying that nobody explains, but once you know why it's happening, it's a lot less alarming.
