When the rainy season ends and the heat begins in earnest, there are uninvited guests who inevitably appear. These are flies and mosquitoes. Many people ignore these uninvited guests, who recur every year, as nothing more than a minor inconvenience during the summer, but if you look closely, they are not something to be taken lightly. It may sound a bit exaggerated, but the U.S. Centers for Disease Control and Prevention (CDC) defines mosquitoes as the most lethal pest to humans. This is because, depending on the region, it is a carrier of various diseases such as dengue fever, West Nile fever, Zika virus, chikungunya, malaria, and lymphatic filariasis. Just because it is a fly is not a place to be at ease. People often treat flies as annoying insects, but when it comes to hygiene, they are not something to be taken lightly. According to a paper published in 2018 by the international academic journal BMC Public Health, more than 100 types of pathogens, including bacteria, viruses, fungi, and parasites, were discovered in just one species of housefly. Considering the habit of flies moving around on garbage and excrement, insect repellent in summer is