Katori Senko: The Japanese Method to Eliminate Mosquitoes at Home During the Summer

These insect-repellent spirals become part of the Japanese landscape in summer.

Katori senko: The Japanese way to eliminate mosquitoes at home during the summer
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Few noises are more disturbing or annoying than those of  mosquitoes buzzing around your bed at night. But even more irritating are the welts left by their bites, which we can't escape from during summer in several places across the world. In Japan, for example, these tiny insects are a real headache. Residents must deal with the tiger mosquito (Aedes albopictus), the most troublesome species on Honshu, the country’s most populous island.

To combat them, savvy Japanese developed a method more than a century ago to help us avoid annoying mosquito bites and the infuriating itch that accompanies them.

Don’t say mosquito. Say katori senko. Burning aromatic plants to repel mosquitoes isn’t a uniquely Japanese practice. However, more than a century ago, the country developed a particularly effective method. Its name: katori senko. It sounds exotic, but the concept is actually quite simple. It consists of a spiral-shaped incense stick attached to a base as well as other ingredients to repel insects, such as Tanacetum cinerariifolium, better known as pyrethrin.

Mosquito coil

A solution with a history. Using the katori senko is very simple. Just light it and wait for the smoke to spread. As mentioned earlier, the burning of aromatic plants is neither new nor exclusive to Japan, but the most popular version of the history of the katori senko claims that it was invented there. More specifically, the credit for the invention goes to Eiichiro Ueyama and his wife, Yuki, who had the idea at the beginning of the 20th century.

The Japan Times recalls that the idea came about purely by chance. In fact, Eiichiro Ueyama wasn’t involved in pest control at all, but rather in the export of tangerines. Through a friend, the politician Fukuzawa Yikichi, Eiichiro met a U.S. trader who offered him some pyrethrum seeds, a colorful plant that, he explained, was deadly to insects. He named it jyochūgiku and soon mixed the powdered flowers with starch to make incense sticks that effectively repelled mosquitoes.

The key: its spiral shape. The sticks were fine, but it was a solution that Eiichiro could have improved. First, they burned very quickly: After 40 minutes, only ashes remained. As such, Yuki, had an idea in 1895: Why not change the shape to a spiral? “The coils were a hit and were hand-rolled until 1957 when production was mechanized. Since then, very little has changed about Ueyama’s Kincho brand-mosquito coils, including the deep green color and the old-fashioned packaging,” the Japanese outlet reports.

The change wasn’t minor. As Living Japan points out, the spiral shape gave the katori senko some essential advantages. First, there was thickness and length, which translated to greater durability. But there were also safety advantages, as the new design reduced the risk of it falling and causing a fire.

Dr. Cameron Webb on X talking on mosquito coils Click on the image to go to the post.

Adapting to the times. The method worked so well that today, we can find mosquito repellents from different brands with various scents. The system has also evolved. According to experts from the University of Sydney, “While traditional coils and sticks were made from a pyrethrum paste, modern mosquito coils mostly contain either pyrethroid insecticides or plant-derived substances such as citronella. They’re cheap, portable, and generally effective at reducing mosquito bites.”

The fine print. The Australian university recalls that coils’ capability to repel mosquitoes “has been well studied” and that they usually “reduce the ability” of the insects to bite. However, it also advises the public to consider their limitations: “The problem is, less nuisance-biting by mosquitoes is good, but when there is a risk of disease, you need to stop all mosquito bites.”

In an article focusing on katori senko, professor Cameron Webb of Sydney Medical School also recommends avoiding prolonged exposure to smoke if people use the coils indoors.

“There’s enough evidence to show that when used outdoors, burning a mosquito coil will assist in reducing mosquito bites, but should be used judiciously. Using them in combination with topical insect repellents probably provides the best protection. Their use in closed rooms is best avoided–‘smokeless’ devices are worth considering as an alternative.”

A good system, but not the only one. Spirals aren’t the only method the Japanese use to protect themselves from mosquito bites. Ultrasonic devices and spray repellents are also common in the country, as well as more traditional tricks, such as installing mosquito nets on windows and doors and eliminating sources of standing water in the home–pots or vases–as much as possible. Japanese residents also, of course, wear clothes that make it more difficult for mosquitoes to bite them.

Image | Tom (Flickr) | Ronald Langeveld (Unsplash)

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