Yes. It has been tested against a wide assortment of insects and been found effective to varying degrees. Thermacell Mosquito Repellents are effective against mosquitoes, gnats, and flies (such as black flies). This isn't surprising since mosquitoes, gnats, and flies are all members of the order Diptera.

How effective are Thermacells?

Studies have shown this chemical to be 95-97% effective at repelling mosquitoes. A single battery charge will operate the Radius for about 6 and a half hours.

Are Thermacells bad for you?

The bottom line is that you have to use it with caution despite having low toxicity for people. This mosquito repellent doesn't only pose very little risk to pets, children, and adults but it's also easy to use and portable.