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How Does Bug Spray Work?

Have you ever been bitten by an insect? You are not alone. Most people you know have been bitten by a mosquito.  

Mosquitoes flying over grass.
(Photo via Shutterstock)

Mosquitoes are the insects that cause the most insect bites worldwide. You might wish for a world without mosquitoes. For a mosquito-free experience, you would have to travel to Antarctica, which is the only place on our planet where mosquitoes do not live.  


Not a favorite 

Even though mosquitoes are probably not at the top of your list of favorite buzzing bugs, they play an important role in the world's ecosystems.  

Mosquito larvae in water.
Mosquito larvae in water. (Photo via Shutterstock)

Mosquito larvae live in aquatic habitats. At this stage in their life, they have limited mobility and make a delicious snack for fish, frogs and salamanders. They also do the important job of filtering water. They eat decaying leaves, and they excrete nitrogen that helps plants grow.  


Adult mosquitoes do not rely solely on blood for nourishment. In fact, only female mosquitoes drink blood, and they only do when they are producing eggs. Like bats, bees and butterflies, mosquitoes feed on nectar from flowers, which makes them excellent pollinators.  


Insects on the hunt 

Why are insects attracted to us? Take a deep breath. Now exhale. You just sent a lung full of carbon dioxide into the air. Insects that hunt, like mosquitoes, use carbon dioxide to detect humans and other mammals. 


Words to know

Excrete: To separate and expel as waste.

Mobility: The ability to move freely or be easily moved.

Nourishment: Food and other substances needed for growth and health.

Pesticide: A substance used to destroy insects and other organisms.   


Carbon dioxide is exhaled with every breath we take, but you can't just hold your breath to hide from mosquitoes. Mosquitoes use olfactory — or smell — sensory receptors in their antennae to find their next meal.  

First, a mosquito senses carbon dioxide from our breath at a distance. As it gets closer, it begins to sense human odor and lactic acid — a key chemical in our sweat. The more you stink, the easier it is for a mosquito to find you! 

The mosquito follows that odor, getting closer and closer. When it gets really close to you, it senses your body heat and lands on your skin or clothing. They can actually taste your skin with their legs while they look for a place to bite.  


Insecticides vs. repellants 

Both insecticides and repellants are considered pesticides. But how do these categories differ? 


Insecticides work in one of three ways:  

  • They kill bugs on the spot. Spraying the chemical directly on the insect disrupts their nervous system, causing them to have tremors or become paralyzed, causing death.  

  • They work over an extended period of time. When insecticide is sprayed on an insect pathway, it allows an insect to come into contact with the spray when they crawl across or ingest it.  

  • They work to reduce their numbers over time. The insecticide could disrupt their ability to reproduce by preventing the insect from laying eggs, or from molting and developing through their life cycle.  

Ant spray, wasp spray and roach spray all contain very similar ingredients. Insecticides are not intelligent. They cannot choose which species they kill. Most insecticides are effective in killing whatever it comes in contact with. Unfortunately, this includes beneficial insects like bees and butterflies as well as birds, fish and small mammals. Insecticides sprayed in our homes, yards and farms to prevent aphids, beetles and other insects from eating flowers and crops can also lead to colony collapse disorder and a decline in honeybees and other pollinators.  

Dead bees covering a white surface.
(Photo via Shutterstock)

It would be quite the challenge and a pretty terrible idea to kill all the bugs around us. We have to find a balance between altering the environment and protecting ourselves from getting bit by an insect. We don’t need to kill the bugs; we just want the insects to leave us alone while we are enjoying the great outdoors. This is a job for insect repellant!  


Repellants repel bugs. Repel means to force something to stop coming toward you. Specially formulated repellants are sprayed on our bodies to prevent bites and stings by covering our skin in a protective barrier that keeps insects at a distance. 

The special ingredients in bug spray are designed to make us less attractive, or invisible, to bugs. They confuse and interfere with the receptors on a mosquito's antennae so they can no longer detect our carbon dioxide, body heat and skin chemicals.  If they can't sense us, they might stay away from us, and then they won't bite us.   

What is bug spray? How does it work? 

Most bug sprays are considered an insect repellant that repels insects from whatever it is sprayed on. Active ingredients in bug spray hide body odors that mosquitoes are attracted to, like carbon dioxide and lactic acid, so the insects can't find you. Often, bug sprays include extra ingredients with smells that bugs don't like to keep them even further away.  

A person wearing a backpack spraying bug spray while standing int he grass next to a line of trees.
(Photo via Shutterstock)

The following active ingredients are approved by the U.S. Environmental Protection Agency as skin-applied repellent ingredients. Some of these ingredients are synthetic, while others are natural.  


DEET: DEET (diethyltoluamide) is a colorless, water-resistant, oily liquid developed in 1944 by the U.S. military and the U.S. Department of Agriculture to help protect soldiers from insects in the jungle. DEET is now the most commonly used, recommended and studied mosquito repellant in the world. One-third of the United States population uses DEET, with 7 million pounds of insect repellant used each year! This synthetic chemical creates an offensive odor and foul taste that deters many biting insects, including mosquitoes, ticks and fleas.  A higher percentage of DEET does not mean it will give you more protection, but it will last longer. Just like a higher percentage of a phone battery doesn't necessarily work better, it lasts for more hours. Repellant containing 15% DEET will give you up to six hours of mosquito protection, while repellant with 25% DEET will last up to eight hours.  According to the EPA, the normal use of DEET does not present a health concern when used properly.  


Picardin: A newer repellant called picardin is an effective repellant, but without the unpleasant odor of DEET. It can be used directly on the skin or clothing to protect against biting insects. The chemicals in this repellant are similar to the natural piperine plant used to make the black pepper you find in your pepper shakers.  


Citronella: Before DEET was invented, citronella was the superior insect repellant. But in a scientific trial, it was determined citronella only provides one hour of protection. Citronella oil is extracted from certain lemongrass plants.  


2-undercanone: No, this isn't what happens when you and your friend tip over while you're paddling in a canoe. This ingredient, also known as methyl nonyl ketone, is often made using artificial materials but can also be made using essential oils from rue, an herbal plant.  


IR3535: This has a super long scientific name: ethyl butylacetylaminopropionate. That’s why they created a codeword for the chemical. This colorless, almost odorless oil comes from a plant from Southwest Asia called the bilimbi fruit tree that produces sour fruit. 


Catnip oil: This plant is irresistible to cats but repels mosquitoes by triggering a chemical receptor that causes pain and itching in insects. This effect is not seen in humans or cats. Studies show the oil from catnip plants is as effective as DEET in repelling mosquitoes.  


Oil of lemon eucalyptus: Oil from the lemon eucalyptus tree is as effective as low-percentage DEET and does not irritate the skin. This oil has a strong smell. This naturally occurring substance has a lower risk than other pesticides, but it should not be used on children younger than 3. 


Other oil extracts like peppermint, basil, rosemary and celery seed can kill mosquito larvae, but the plants themselves do not repel flying mosquitoes.  


Because mosquitoes are more attracted to darker colors, wearing light-colored clothing is a good choice. Mosquitoes can sting you through clothing, so loose-fitting, tightly woven materials are best. Some clothing also comes pretreated with insect repellant. These clothes can be washed and still be effective. You can also retreat these fabrics. 


Don't bug out! Use bug spray the right way  

A water bottle, sunglasses, hat, map and bug spray laid out on the grass.
(Photo by Brittany Schaller)

Here are some tips to ensure you use bug spray correctly. 

  • Always use bug spray under adult supervision. 

  • Follow directions carefully. Do not use more frequently than directed.  

  • Apply bug spray outdoors — never inside. You do not want to inhale the spray.  

  • Never apply bug spray to your face.  

  • Spray bug spray on clothes and exposed skin. You don't need to spray the skin underneath your clothes. One layer of protection will do the job!  

  • Clean bug spray off your body when you no longer need it. Take a shower or wash your arms and legs. Do not leave bug spray on overnight.  

The spring and summer months are filled with potential for outdoor adventures. It is important to prepare and make sure you have all the gear you need to ensure you have a safe and fun experience. Sunglasses, a hat, a water bottle, a map and don't forget the bug spray! 


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