There is no scientific evidence that ultrasound keeps mosquitoes away or prevents them from biting. However, there are various gadgets and some mosquito repellent apps that claim to do just that.

We tested one of these anti-mosquito apps in a cage with 200 female yellow fever mosquitoes (Aedes aegypti) and the result is very clear: Patrick, our brave mosquito breeding specialist, holds a smartphone with the anti-mosquito app switched on in the cage. Within a few seconds, his hand and forearm are completely bitten!

For comparison, he treated his arm with an effective mosquito spray (30% DEET) and held it in the cage. A few mosquitoes land briefly on his arm, but fly away again without biting.