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(photo Source: Pixabay) Summer is coming, along with buzzing mosquitoes. As the saying goes, everything has a spirit, except mosquitoes and cockroaches. In order to expel mosquitoes, people at all times and at home and abroad have thought of a lot of ways.

(photo Source: GIPHY) from a long time ago, people in China have burned "rough grass" and "Jiacao" to ward off mosquitoes, and they are considered to be the earliest "mosquito incense". Until now, some people have smoked moxa sticks to ward off mosquitoes, and studies have found that Artemisia argyi contains cineole, terpineol and other substances, which are unpleasant ingredients for mosquitoes.

Westerners also have a variety of ways of repelling mosquitoes. Cow dung, coconut shells and coffee grounds have all been burned. Some people believe that bathing with lilac can ward off mosquitoes. Some people even think that as long as they drink gin, they will not be afraid of being bitten.

To say which mosquito repellent is the most reliable, it still depends on professional mosquito repellent. But which ingredient in insect repellent plays a key role?

(photo source: see watermark) at present, the scientifically proven and effective mosquito repellent ingredients include DEET, ICARIDIN, also known as icariin, piperidine, piperidine, and so on. Scientists have found that they work in different ways: DEET can prevent mosquitoes from biting and Eccaridin can prevent mosquitoes from approaching.

DEET: the feet of mosquitoes don't like DEET has been considered one of the most effective insect repellents since the 1940s, but how it works has not been clear. Until a study discovered the secret between DEET and mosquitoes.

DEET may not smell bad to some mosquitoes. a mutated mosquito even prefers the smell of DEET, but when it lands on the skin coated with DEET, it flies away.

DEET is slightly toxic, so don't swallow it. Avoid the eyes, mouth and nose when spraying DEET (photo source: GIPHY) scientists speculate that this is because mosquitoes' feet don't like the smell of DEET, and when they land on the surface of DEET-protected skin, they are frightened by the disgusting smell in the face, so they turn around and run.

Mosquitoes have taste receptors on their feet and mouthparts, so once they land, they can taste the host. Not only mosquitoes, but other insects also have taste receptors on their feet, such as flies "rubbing their hands" in order to clean up the dirt and make it easier to use the taste receptors on their feet to better distinguish food.

To test this theory, Emily Emily Dennis, a neurogeneticist at Princeton University, contributed several big bags. She wore a pair of gloves on her hands and cut them so small that they could only be touched by the mosquito's legs or mouthparts and could not fall on the skin at the same time.

Emily was bitten when only the mosquito's mouthparts landed on the skin coated with DEET, so it can be inferred that the mosquito's mouthparts could not taste DEET.

(photo source: GIPHY) verifying whether mosquitoes can taste DEET on their legs is a very delicate task. Emily wrapped the mosquito's legs in a gel that only acts as a barrier. Mosquitoes with all their legs covered will still bite her, but even if there is no gel on one leg, it can make the mosquitoes fly away immediately after landing.

Emily can finally come to the conclusion that the taste receptors on mosquitoes' feet hate DEET.

After experiments, the researchers found that the effective time of insect repellent containing 10% DEET was 2 hours, and that of 24% was 5-10 hours, but more than 50% did not significantly prolong the effective time.

Daily use content is less than 10%. If you go to places with more mosquitoes, you can choose products with a concentration of 10% and 30%. It is not recommended for children under the age of 12 to use products with a concentration of more than 30%.

Eccardine: odor invisibility cloak in order to find fragrant humans, mosquitoes use a combination of vision, taste, smell and thermal perception.

We can release carbon dioxide by breathing, and the sweat glands and pores on the skin can also release some of the excess carbon dioxide from the body. The sebum, sweat and gas we secrete will mix into a "human smell" and float into the air.

Mosquitoes can detect carbon dioxide from nearly 10 meters away, then fly closer to the smell, then begin to feel human body temperature, accurately locate and land on our skin.

(photo Source: GIPHY) the study found that Ecaridin solution is also very effective against mosquitoes. Its working principle is that it can be mixed with human odors, and when odor molecules reach mosquitoes' olfactory receptors, they do not attract their attention.

So if you spray mosquito repellent containing Eccaridin, mosquitoes probably won't find us at all, just like wearing an "odor invisibility cloak".

The recommended concentration for daily use is 5% 10%, which can provide protection for 3% to 5 hours; the concentration of 20% Ecaridine repellent can provide protection for up to 8 hours and 12 hours.

Other more effective ingredients include mosquito repellent ester (IR3535), lemon eucalyptus oil (OLE), menthol-3 mint 8-diol (PMD), etc. (children under 3 years old should not use products containing the latter two ingredients, do not use any insect repellent for babies under 2 months old, use physical methods to prevent mosquitoes), you can pay attention to it when choosing and buying.

Some friends may have noticed that we are less likely to be bitten by mosquitoes when the air conditioner is on. This is because mosquitoes are very sensitive to temperature. When the temperature is below 25 ℃, the activity of mosquitoes decreases.

In addition, when we turn on the air conditioner, we sweat less and give off less flavor, so it is not easy to be detected by mosquitoes.

Other studies have found that mosquitoes really don't like the taste of coconut, and if you use soap with coconut fragrance, it may be more beneficial to mosquito prevention.

Reference:

[1] https://www.npr.org/sections/goatsandsoda/2018/06/30/623865454/a-guide-to-mosquito-repellents-from-deet-to-gin-and-tonic

[2] https://www.cdc.gov/mosquitoes/mosquito-bites/prevent-mosquito-bites.html

[3] https://www.livescience.com/65334-how-does-deet-work-mosquitos.html

[4] https://en.wikipedia.org/wiki/Icaridin

[5] https://www.cell.com/iscience/fulltext/S2589-0042(23)00744-7

[6] Hua Dan Dan. Purification of Artemisia extract and its application in insect repellent and mosquito repellent functional textiles [D]. Suzhou University, 2014.

This article is from the official Wechat account: bring Science Home (ID:steamforkids), author: everything Magazine

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