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Using lasers against mosquitoes: Will a dream soon come true?
by Martin Jungfer
Testing the Thermacell E55, a mosquito repeller that actually works
21.8.2025
Translation: Katherine Martin
Pictures: Martin Jungfer
Camping holidays tend to come with a challenge: fighting off the local mosquitoes. This year, however, I managed to stay pretty much bite-free. The Thermacell E55 fared well in this hands-on test.
Let’s get one thing out of the way first. Yes, the Thermacell E55 is a chemical-based mosquito repeller. Of course, you’re free to opt for natural remedies such as coffee powder, eucalyptus or lemon oil. Alternatively, you could protect yourself by wearing long-sleeved tops and trousers, or hope that ultrasonic repellers will do the trick. While some of these methods might be slightly effective, ultrasound anti-mosquito gadgets are scientifically proven to have no effect. Meanwhile, defensive lasers that zap mosquitoes out of the air are, at best, a pipe dream.
What I want now is the best possible anti-mosquito protection without having to shower in «Anti-Brumm» spray. For several years now, I’ve been using an older Thermacell device that works with gas cartridges and active ingredient mats. You can read about it in my 2021 review:
How does the Thermacell E55 work?
Now that Thermacell’s come up with a new gadget, I want to know whether it’s better or just different. Basically, the E55 model is similar to its predecessor, the Halo Mini. It heats and vapourises an active ingredient, creating what’s essentially a cloud around the device. That active ingredient in the air then keeps mosquitoes away. According to Thermacell, the «protection zone» formed around the device measures up to 29 square metres.
The E55’s integrated battery pack provides the heat it needs to vaporise the liquid active ingredient, a solution containing the insecticide metofluthrin. The chemical confuses mosquitoes, anaesthetising and, ultimately, killing them. In a 2017 study exploring the metofluthrin’s effects, the «biting activity» of yellow-fever mosquitoes in a closed room was significantly reduced «within a short period of time».
I managed to catch one of the critters at least half alive near the E55. The neurotoxin had clearly affected the insect, making it uncoordinated and weirdly twitchy.
Is metofluthrin dangerous?
On the E55’s active ingredient cartridge, you’ll find a warning sticker with a pictogram of a corroded lung and a dead fish. The specialist literature describes metofluthrin’s «neurotoxic potential». Tests have demonstrated that the substance causes strong tremors in rats. If dogs come into direct contact with the chemical, they respond by salivating more. The chemical’s also highly toxic to bees, fish and aquatic invertebrates such as mussels and snails.
In practice, however, the Thermacell EFF is safe to use. The device has been tested by US authorities and has EU approval. Only a small amount of the chemical evaporates from the device while it’s being used. And besides, hopefully nobody would decide to sniff the vapours coming out of it.
What’s the E55 repeller like to use?
While it certainly doesn’t hurt to take a glance at the instructions, you basically can’t go wrong when setting up the E55. In the box, you’ll find the device itself. Its shape and dimensions remind me of an urn. In hindsight, maybe I shouldn’t have gone for a black one. Mind you, as of August 2025, it’s the only colour available in our range. Thermacell, however, also sells the E55 in a slightly more cheerful dark blue.
The device has a magnetic lid, which is easy to take off. There’s a recess for slotting in the active ingredient cartridge that comes included with the E55. It contains 10 millilitres of liquid, which is supposed to give you 40 hours of use. The device easily achieved that during my review, managing about 50 hours before it conked out.
Bear in mind there are at least two different sizes of refills on the market: for 12 and for 40 hours of use. I’d recommend going for the larger version if you can find it, as it’s better value for money. Unfortunately, we currently only stock the small cartridge.
And yes, Thermacell basically traps you into a cycle of follow-up costs. Buying the device is a really low, one-off investment. But in order to actually use your purchase, you need to buy the refill cartridges regularly. This generates sales for Thermacell and, unfortunately, quite a lot of plastic waste too. Since the cartridges aren’t refillable, they end up in the bin.
When you’re not using the E55, you should take out the cartridge and put the little cap back on. That way, you’ll avoid unnecessary vaporisation from the wick.
Once the cartridge is in and the lid is back on, you hold down the only button on the device for about two seconds. You’ll hear three ascending tones to confirm that you’ve switched on the E55. A ring of four LEDs around the power button start to flash, meaning the device is heating up. In just under 15 minutes, the E55 reaches its operating temperature, and the LEDs stop flashing. If you look closely, you’ll be able to see a small cloud of steam coming out of the top – like a genie coming out of a bottle to fight off the mosquitoes.
Thermacell promises its device will run for five and a half hours if it’s been fully charged via the USB-C cable. In practice, it genuinely does fulfil its promise. A three-stage status display under the power button shows you how full the battery is. If three LEDs are lit, the battery’s full. If only one is lit, you’ll soon lose your mosquito protection. Once the last light starts flashing red, the device has 20 minutes of runtime left.
During my review, I also hooked the device up to a power bank. It’s just as well that you can charge the E55 while it’s in use, as it takes around five hours to recharge an empty battery.
The port for the cable is covered with a rubber cap, and needs to be folded out before the cable goes in. Once I’d done that a few times, the cap just hung there limply. This is unnecessarily sloppy design.
How effective is the Thermacell E55?
Rather than testing the E55’s effectiveness in a lab, I put it through its paces in everyday situations. More precisely, I left it to do its thing on our breakfast table, which we’d set up in an open seating area between some trees and bushes. After a night of rain and a morning temperature of 25 degrees Celsius, it should’ve been a paradise for mosquitoes. However, the Thermacell repeller successfully kept the bugs away.
Testing the device that evening in the campsite restaurant didn’t go quite as well. Shortly after sunset, we came under attack from a mosquito squadron. At every table, diners were slapping bugs off their faces or off the shoulders of their companions. It was the same story at our table. If you have a tendency to sweat more than the average person, your presence will definitely be counterproductive to the device. Sweatier folks apparently smell so enticing to mosquitoes that the bugs will fight their way through the cloud of chemicals, often using the last of their strength to bite before turning away and dying. The only protection against these kamikaze tactics would be a mosquito net.
Windy days also reduce the device’s effectiveness, as the active ingredient evaporates immediately as soon as the vapours come out. The best thing to do in that situation is to position the device so that the vapours are carried by the wind to the place where you want to be protected.
Update (26 August 2025): The E55 is currently unavailable on Galaxus, and will remain so for the foreseeable future. It’s currently unclear whether the device has been approved for the Swiss market. Our purchasing team is in the process of clarifying this. Once they’ve done that, the product will become available again. We apologise for the inconvenience.
In a nutshell
Helps keep mosquitoes at bay, but doesn’t work miracles
You can’t smell it, you can’t see it, but the E55 effectively keeps mosquitoes away. Not only is it a nice alternative to sprays you’d apply directly onto your skin, but it actually works. Once the device had kicked into gear and created a protective shield of metofluthrin vapour around me, I was genuinely well protected. That being said, having the E55 nearby doesn’t give you a 100 per cent guarantee of getting through the day and night without being bitten. Cracks open up in the device’s defence if the vapours are swirled around too much or if the smell of sweat proves too tempting for the bugs.
Pro
- Suitable for air travel (unlike Thermacell devices with a gas cartridge)
- Cartridge lasts pretty long (40 hours)
- Can be used while it’s charging
- Rechargeable with a USB-C cable
- Integrated battery
- Effectively keeps mosquitoes at bay
Contra
- Slow to charge
- Expensive cartridges
- Impractical shape
Martin Jungfer
Head of Content
Martin.Jungfer@digitecgalaxus.chJournalist since 1997. Stopovers in Franconia (or the Franken region), Lake Constance, Obwalden, Nidwalden and Zurich. Father since 2014. Expert in editorial organisation and motivation. Focus on sustainability, home office tools, beautiful things for the home, creative toys and sports equipment.
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