The Complete Guide To Mosquito Repellents [Week 24]

Posted On August 26, 2021

You want to enjoy the rest of the summer without getting itchy welts from mosquito bites, but which mosquito repellents are healthy for you and the environment?

Amanda Drews, 9 minute read

It’s the summertime and you want to sit around the campfire, roast some s’mores and enjoy the warm nights under the stars. One problem. Those pesky mosquitos are just waiting for you to come out so they can feast.

Ok, that’s a little dramatic.

Or is it? Mosquitos are the world’s deadliest animal and kill hundreds of thousands of people a year from diseases such as malaria, dengue fever, Zika, West Nile, yellow fever and more (WHO). Depending on where you live, the time of year and the rates of infection, mosquito bites may range from bothersome to deadly. Here in Minnesota, we joke about mosquitos being the state bird (it’s actually the common loon just FYI), but it’s no laughing matter once those suckers start biting. It just plain sucks.

As our climate warms and mosquitos expand both their territory and breeding season, we will need proper defenses against them. Let’s find out what works and what doesn’t in the fight against mosquitos.

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Why me?!

You may sometimes feel like you’re the only person getting bit by mosquitos in a group of people. You might be right.

Researchers think mosquitos are attracted to certain people for a few different reasons.

• Carbon dioxide (CO2) output– Mosquitos use CO2 to recognize and seek hosts. The breath coming out of living things attracts them and draws them in (The Royal Society Publishing)
• You’re pregnant– Congrats! But of course this is probably the time when you do not want to get bit as much. Thoughts are that pregnant woman exhale more CO2 and have a higher body temperature than non-pregnant women (NCBI).
• Movement– Motion in general is not only going to cause you to breathe heavier but it’s a way of advertising where you are to mosquitos.
• Dark clothing-Mosquitos are generally attracted to black objects (Journal of Experimental Biology).
• Alcohol consumption– A small study found a significant difference in mosquito attraction to people that were drinking (NIH). I couldn’t find the whole study though so it would be interesting to see the controls. Were those people more likely to be talking loudly or moving around? Were they just chillin’ or were there conga lines involved?
• You just smell dang good to them-There may be a big combination of factors such as genetics, body odor, blood type and more. Different species of mosquitoes also seem to prefer certain things as well. So a non-pregnant, still sitting, lightly breathing, sober person wearing light clothing could still attract just as many mosquitoes as someone who is the exact opposite. Well, hopefully not drinking heavily and pregnant.

How can you avoid getting bit and keep mosquitos away?

There are several ways to minimize the amount of mosquitos you come in contact with.

• Head inside-Avoid mosquitos all together by heading inside when they are active.
• Cover up-Throw on some loose fitting, long sleeves, pants, socks, and shoes if you plan on being outside when mosquitos are active, especially during dawn and dusk.
• Keep windows and doors closed– Keep them out of your house in the first place. If you have the AC on this will help you save energy as well. Prefer a fresh breeze? Invest in some screen doors and windows.

• Eliminate mosquito breeding grounds– Take a walk around your yard and identify any pools of water where wrigglers could be living (that’s the name for little mosquito larvae!). Check potted plants, toys, fill low spots in the yard with compost and keep bird baths clean.

• Make a mosquito predator friendly yard– Dragonflies, birds, bats, spiders, damselflies, turtles, frogs and tadpoles are all known to eat mosquitos or their larva. Put up a bat or bird house! Insectivorous bats usually go for moths but they will nab a few mosquitoes here and there as well. Dragonflies prefer higher plants for perching on. Planting swamp milkweed, Joe Pye weed, and black-eyed Susans will attract prey for the dragonflies.

• Can you use certain plants to deter mosquitos from your yard?– There are many different types of plants such as the citronella geranium, floss flower, citrosum, marigold, eucalyptus, peppermint, lemon balm, catnip, basil, thyme, mint, and lavender that are said to ward off mosquitos. The catch is, they aren’t going to do anything just sitting there. They would have to be crushed up to be effective. So while there’s probably no harm in planting these, don’t expect results unless you plan on making some DIY mosquito repellant with them.
• Use an insect repellent spray-Let’s talk about this more below.

Insect Repellents

Hundreds of products are out there claiming they will repel mosquitos but not all of them can live up to the results they promise.

There are also many concerns that people have in regards to their health and what they are spraying on themselves. The American Academy of Pediatrics recommends that children under 2 months should not be exposed to DEET and kids under 3 years old should not be exposed to repellents with oil of lemon eucalyptus (OLE) or para-methane-diol (PMD). It may cause allergic skin reactions and it just hasn’t been studied enough yet.

Health Concerns

DEET

Let’s concentrate on talking about DEET first since it is the most commonly used and most effective mosquito repellent. Scientists think DEET, or N,N-diethyl-meta-toluamide, works by making us taste or smell bad to mosquitos with the chemical receptors on their feet. (This is one way many insects smell!) This means that the mosquitos may briefly land on DEET covered skin but they shouldn’t bite. Typically they will stay away all together as well as ticks, flies and other pests.

DEET repellents come in varying concentrations. The higher the concentration, the longer it should be effective at repelling mosquitos. However, with higher concentrations you also get increased odor and it can damage fabrics and plastics. There are varying reports of where effectiveness plateaus (usually between 30 and 50 percent concentration according to sciencing.com). In general, choose a concentration under 30% that matches about how long you typically need protection for. Apply sparingly and only to the exposed patches of skin. Stanford Children’s Health says products with 24% DEET should last around 5 hours.

The EPA has ruled DEET as safe for both adults and children when used properly and they have “not identified any risks of concern to human health, non-target species or the environment” after a 2014 interim review under the Registration Review Program. However, it appears they are still waiting on results from an Endocrine Disruptor Screening under the FFDCA section 408(p) but have other chemicals prioritized.

DEET has been marketed since the 1950’s and since then there have been a few reports of neurological events after the use of DEET as well as cases of ingestion. You can read the CDC report here but it also emphasizes that millions of people utilize DEET daily as an insect repellent without reported adverse health effects.

Proper use of DEET includes not spraying DEET directly onto faces, on cuts, open wounds or in enclosed areas. It is recommend to wash off DEET from skin and clothing once you are back indoors. Never allow children to apply or ingest DEET. It should not be applied to skin that will be covered by clothing. The EPA considers DEET in Category III (slightly toxic) for toxicity “by the eye, dermal and oral routes.” Note that this is the second lowest out of four categories of toxicity right under Category IV-practically non-toxic.

There have been studies suggesting the combination of sunscreen and DEET can lead to adverse health effects. The sunscreen in the study seemed to concentrate on the interaction of the DEET with oxybenzone and how their combination could lead to increased chemical absorption through the skin. We know from our Complete Guide To Sunscreen from Week 22 that oxybenzone is the number one thing we want to avoid in our sunscreens anyways. I haven’t found studies on oxybenzone-free sunscreen interactions with DEET. Overall, it’s best to avoid combination sunscreens and insect repellent as sunscreen needs to be reapplied often and repellents are meant to last many hours longer.

Picaridin

A relatively new product to the United States is Picaridin/ KBR 3023. While DEET is meant to be applied to skin only, Picaridin can be applied to both skin and clothing. In addition to mosquitos, ticks and flies, Picaridin also repels fleas and chiggers (National Pesticide Information Center).

IR3535

Insect Repellent 3535 (or Merck 3535 or ethyl butylacetylaminopropionate) is recognized by the EPA as safe for both children and adults but cautions that it is an eye irritant. IR3535 has the added claim of protecting against head lice on their website. I couldn’t find any actual IR 3535 mosquito repellent products for sale.

Environmental Impacts of Repellent Use

Each type of mosquito repellent uses different ingredients and chemicals to do it’s job. Some of these compounds may work well, but not be so great for the environment.

• DEET– Properly used, DEET is virtually nontoxic to mammals but is slightly toxic to fish, birds and aquatic invertebrates. DEET doesn’t break down well in the soil and can leach into groundwater but isn’t thought to be a “persistent or bioaccumulative substance“. So when used properly, there shouldn’t be much of an issue.
• Picaridin has been found to be moderately toxic to fish because it can build up in their tissues.
• Merck claims IR 3535 is not toxic to aquatic organisms. It is thought that it is not a threat to groundwater because it breaks down from the bacteria found in soil.
• Metofluthrin, which is found in some clip-on or coiled area repellents and is part of the group of chemicals known as pyrethroids which are highly toxic to both freshwater and estuarine/marine fish and invertebrates (EPA, 2016).
• Permethrin, which you can use to treat your clothing with or even buy permethrin factory-treated clothing, has the same effects as the metofluthrin on aquatic life. Specifically trout and little baby lobsters. The EPA has no health advisories against using permethrin treated clothing even for pregnant or breast-feeding women, and children. There isn’t much concern about effects on the environment though from the International Programme on Chemical Safety as they deem permethrin as having very little movement in the environment and that it’s “unlikely that it will attain significant levels in the environment”. Basically it is frowned upon to go walking in a stream with permethrin treated pants.
• Spraying and fogging– Sure spraying your yard with repellent will kill whatever is in it at the moment but it will also harm every other little insect in the yard as well, like pollinators such as butterflies and bees. And guess what?! Other mosquitoes will fly into your yard after spraying dissipates because they can travel a couple miles (The American Mosquito Control Association).
• Aerosol sprays– I typically try to avoid any types of aerosol sprays since they contribute to asthma inducing smog by emitting volatile organic compounds (VOCs). So when you have the choice to use a pump or an aerosol, I’d go with the pump.

Does mosquito repellent expire?

If you are using a DEET or picardin product, there shouldn’t be an expiration date but it’s probably best to throw it out after 10 years as it will loses it’s effectiveness. If it’s an IR3535 product, it expires after 18 months (pestcontrolfaq.com).

1. Learn about the potential diseases mosquitos and ticks carry in your area.
2. Decide what level of protection you and your family needs from mosquitos and choose a repellent that meets your needs.
3. Take a walk around your house and identify any areas that may hold standing water that will attract egg laying mosquitos. Dump those out and see if you can prevent it from filling in the future.
4. Check out Week 25 for reviews on Mosquito Repellents.

Medical disclosure: I’m not a doctor. Do not take any of my recommendations as official medical advice. A Greener Demeanor makes no warranty as to the accuracy or reliability of any information obtained through the site or that a product or method will meet your expectations. Use products at your own risk. Consult your own doctor for medical advice.