With the summer months comes more time spent outside. Backyard get togethers, camping or sitting by a bonfire is always great until we notice the bugs joining us.
Along with mosquitoes, ticks and outdoor bugs being a nuisance, they also can carry some pretty scary viruses.
Obviously we need to protect ourselves, but many of us are concerned with the ingredients of regular bug sprays and insect repellents.
One of the ingredients used often is DEET. When it’s used frequently and heavily, it has been linked with skin irritation, respiratory effects, rashes, and even neurological effects. The chemical is particularly concerning in children, where in rare cases, it can lead to lethargy and headaches. In pregnant women, if used on bare skin, it could harm the baby.
The History of DEET
Chemically called “diethyltoluamide,” DEET is prepared by converting 3-methylbenzoic acid to acyl chloride and allowing it to react with diethylamine. It was developed for Army soldiers going through jungle warfare in WWII. Before that, farmers used it as a pesticide on fields. By the year 1957, manufacturers were selling insect repellents containing DEET to the general public.
The repellant is believed to work because insects don’t like the smell of it, and also because it may “blind” them to scents produced by human sweat and breath that typically are attractive to pests. However it works, studies have shown that it definitely does, repelling insects for up to 12 hours when applied at 100 percent.
Later studies, however, reported some concern about the chemical and how it may affect skin and internal health. Manufacturers now advise users to avoid applying the product to broken or damaged skin, or under clothing, and to wash it off after it’s no longer needed.
How DEET May Affect Skin and Overall Health
A 2014 report by the Environmental Protection Agency (EPA) stated that DEET “continues to meet safety standards based on current scientific knowledge.” They added that “normal use” doesn’t present a health concern to the general population, including children, but advised consumers to “read and follow label directions.”
The Centers for Disease Control and Prevention (CDC) basically agrees, though they warn that “conservative use of low-concentration DEET products is most appropriate when applying repellents to children, and DEET should not be used on children younger than 2 months of age.”
General side effects of DEET may include:
- Skin irritation (irritation, redness, rash, swelling).
- Eye irritation (if you mistakenly get it into your eyes), including pain and watery eyes.
- Stomach upset, vomiting, and nausea, if you mistakenly swallow it.
- Neurological effects, such as seizures (at higher and consistent exposures).
DEET can get inside the body when you apply it to your skin. If the product contains alcohol as well, that can improve penetration, so that more gets into the bloodstream. Health experts warn that sunscreens containing DEET should be avoided because they cause more DEET to sink inside the body.
The CDC also lists a number of studies that raised concerns about how DEET could affect health. Here’s a glimpse of those, along with a few other related studies:
- Skin effects in soldiers: A small number of soldiers who applied military-issued DEET repellents suffered serious side effects on the skin, including burning sensations, blisters, reddening of the skin, and scarring. In a controlled test, 63 soldiers applied a gauze pad soaked in DEET to the skin on the inside of their elbows. Nearly half—46 percent—developed a reaction to the treatment. Researchers advised users to always wash the DEET off their skin before going to sleep.
- Skin and respiratory effects in National Park Service employees: In a study on National Park Service employees at Everglades National Park, researchers found that about 25 percent of workers using DEET reported health effects. These included rashes, skin or mucous membrane irritation, numb or burning lips, dizziness, disorientation, and difficulty concentrating, as well as headaches and nausea.
- More skin effects: An analysis of all DEET calls into poison control centers between 1993 and 1997 found that 10.5 percent involved skin symptoms like irritation and rash. Another 21 percent involved eye effects, when users mistakenly got the chemical into their eyes.
- Brain effects: A 2002 animal study by Duke University researchers found that frequent and prolonged use of DEET caused brain cell death and behavioral changes. The chemical actually caused neurons in the brain to die—affecting regions of the brain that control muscle movement, learning, memory, and concentration. Rats exposed to an average human dose of DEET performed far worse than control rats on tasks requiring muscle control, strength, and coordination. “If used sparingly,” said Mohamed Abou-Donia, lead author of the study, “infrequently and by itself, DEET may not have negative effects—the literature here isn’t clear. But frequent and heavy use of DEET, especially in combination with other chemicals or medications, could cause brain deficits in vulnerable populations.”
- Neurotoxicity in Gulf War Veterans: After 30,000 Persian Gulf War veterans complained of neurological symptoms of unknown cause, researchers tested the chemicals they were exposed to during the war—which included DEET—on chickens. They found that hens exposed to a combination of three chemicals (DEET, an anti-nerve agent, and another insecticide) showed similar neurological side effects on the brain. Researchers noted that exposure to only one chemical alone didn’t have the same effect.
- Effects in children: This is where DEET gets especially concerning. Children are likely to put their hands in their mouths and near their eyes and noses. If those hands are covered in DEET, that gives the chemical an easy entrance into the body. The CDC notes that though rare, reports of toxicity from DEET in children can include symptoms like lethargy, headaches, tremors, seizures, and convulsions. Accidental ingestion can result in loss of muscle control, loss of consciousness, and seizures. In one case, for example, a 6-year-old girl ended up in the hospital because she couldn’t control her body movements. It turned out she had been exposed to a spray containing 15 percent DEET over extensive areas of her skin on more than 10 occasions. In the summertime, that’s not totally unheard of, so the case serves as a good caution to parents.
- Effects in pregnant women: While extremely rare, there have been a handful of reports of DEET use in pregnant women resulting in birth defects in the infant children. A 2001 study found that DEET applied in the second and third trimesters resulted in an 8 percent DEET concentration in the blood—indicating that it had crossed the placenta.
Because of these and other concerns, the CDC recommends using a DEET concentration of 30 percent or less, and advises “conservative use” of a low-concentration product in children.
The American Academy of Pediatrics also advises that children under the age of 2 months not be exposed to DEET, and that any product containing DEET be applied to any other children no more than once a day, and even then, not around the eyes or mouth.
In addition to its potential effects in humans, DEET has also been detected at low levels in 75 percent of streams sampled, where it could potentially affect drinking water.
For everyday insect avoidance, though, most of us would like to use something safer to protect our families from summer pests.
Fortunately, there are some essential oils that can help keep bugs away. We’ve got six of them here, along with recommendations for how best to use them. We are also sharing a recipe for making your own natural bug repellent (scroll to the bottom for the recipe.)
Natural Insect Repellents
Why would essential oils and other natural ingredients repel bugs?
They are made up of chemicals stored in the plant. In many cases, these chemicals work to repel predators—often the buggy kind. When we extract these oils from the plant, we can put them to work protecting us, instead.
Developing countries still use bruised plants in their houses to ward off pests. (They bruise them to release the oil and aroma.)
We like using oils because we know they’re natural and don’t include the synthetic chemicals that standard repellents may contain. They are less likely to cause skin irritation and reactions, and aren’t a threat to our internal health.
Not all essential oils work against pests, however. In fact, according to the research found so far, only a select few are truly effective, and each of these may differ in which bugs they are best at scaring away.
The active ingredients in essential oils also tend to be highly volatile, so they may be effective for only a short period of time (usually about an hour). After that, they evaporate and leave the user unprotected. Frequent reapplication is often necessary.
1. Oil of Lemon Eucalyptus
After DEET and picaridin (a synthetic compound recommended by the World Health Organization for protection against mosquito-borne diseases), the EWG recommends oil of lemon eucalyptus. (They note that natural lemon eucalyptus oil is not the same as oil of lemon eucalyptus, so be careful.)
This is a repellent that originated as an extract of the lemon eucalyptus tree native to Australia. Lemon eucalyptus essential oil is comprised of 85 percent citronellal—a compound (terpinoid) found in citronella, rose, and geranium oils.
Some insect repellents already carry PMD (paramenthane-3,8-diol), which is the active ingredient in oil of lemon eucalyptus. Some combine the two—PMD and the extract.
The Environmental Protection Agency (EPA) has listed this ingredient as effective against mosquitoes and other insects, though it’s considered about half as effective as DEET. Higher concentrations of PMD, however, can increase its effectiveness, with a 30 percent PMD product being about as good as a 15 percent DEET product, though its protection time is shorter. (You may need to reapply more often.)
Effective against: Mosquitoes and ticks, but not sand flies or “no-see-ums.” It also evaporates more slowly than most essential oils and will last for several hours. PMD is the only plant-based repellant advocated for use in disease endemic areas by the CDC.
2. Oil of Citronella
Citronella oil is obtained from the leaves and stems of lemongrass, and produces the compounds citronellal, eitronellol, and geraniol, which are all used in perfumes, candles, and soaps.
The oil has also been registered as a plant-based insect repellant in the U.S. since 1948. It’s already found in a number of commercial insect repellents and even some sunscreen products. Instead of scaring away insects with its scent, it seems to mask other scents that are attractive to them, making it difficult for them to locate their targets.
Studies have shown that citronella is effective, especially when combined with vanillin (the essential constituent of vanilla) to extend protection times. In a 2011 review of eleven studies, citronella protection times were lower than DEET, but combining the oil with vanillin helped increase those times. The two together were found to repel mosquitoes for at least three hours.
Effective against: Mosquitoes and other flying insects. If using alone, reapply every 30 minutes. Be aware that it is a skin sensitizer, and can cause allergic reactions if used on bare skin.
3. Catnip Oil
Keep the cats away—this repellent is for humans!
Catnip oil, extracted from the catnip plant, was found in a 2001 study to repel mosquitoes more effectively than DEET. This was only one study, so the results should be taken with caution, but they are promising.
Researchers put groups of 20 mosquitoes in a glass tube, half of which was treated with catnip oil (nepetalactone). After 10 minutes, only an average of about 20 percent (4 mosquitoes) remained on the side treated with a high dose (1.0 percent) of the oil, and only about 25 percent (5 mosquitoes) in the low-dose (0.1 percent) side. The same tests with DEET resulted in 40-45 percent (8-9 mosquitoes) remaining on the treated side.
A later 2006 study found similar results, with catnip oil being the most effective (among thyme, amyris, eucalyptus, and cinnamon), providing six hours of protection at two different concentrations. Thyme was also effective, but lasted only two hours.
Finally, a 2011 study also found the oil effective against mosquitoes and ticks.
Effective against: Mosquitoes, ticks, and potentially other flying insects.
4. Neem Oil
A number of studies have shown that neem can help protect you from mosquito bites. In the late 90s, researchers in India found that kerosene lamps with one percent neem oil reduced bites on volunteers sitting in a room overnight.
Another study found two percent neem oil mixed with coconut oil and applied to the skin protected against a variety of mosquitoes, ranging from 96-100 percent protection against malaria transmitting types, to 61-94 percent protection against West Nile virus types.
Effective against: Mosquitoes, and possibly other flying insects. Most effective when combined with a carrier oil and applied to the skin. Less effective in sprays. Reapply regularly.
5. Soybean Oil
There is some evidence that this oil may provide longer-lasting protection than other natural repellants, particularly citronella.
In a 2004 study, Bite Blocker, which contains two percent soybean oil, protected against mosquito bites for 5-7 hours—longer than other options.
An earlier 2002 study found that soybean oil on its own protected against mosquito bites for an average of 94.6 minutes—longer than most oils on their own. And a 2011 study used a number of other essential oils mixed in soybean oil for repellant tests, showing that soybean oil may be the best choice for homemade insect repellant mixtures.
Lemongrass (citronella) has also been found to be protective when mixed with soybean oil—another good idea for homemade solutions.
Effective against: A variety of mosquitoes, and potentially other insects.
6. Cedar (Nootkatone)
If you’re looking for protection against ticks and other creepy-crawlies, be sure to include cedar in your mixture.
In a 2014 study, cedarwood oil was significantly effective against ants, red fire ants, and black-legged ticks. At the highest dosage (6.3 mg/ml), it killed 100 percent of the ticks. An earlier 2011 study also found the oil to be effective at repelling two species of ticks.
If you’re looking for a flea repellant for your dog, this oil may also be a good option. (Apply on a daily basis.) It not only kills fleas on contact, but can help heal itching and hot spots. Simply rub on your hands and run through the animal’s coat, or apply with a spray bottle.
Effective against: Ticks, ants, fleas, mites, lice, and other creepy-crawlies.
Some Other Oils that May Be Effective
There are a number of other oils that may provide short-term protection as repellents, but so far, these have shown to last only a short time, or to be less effective than those listed above. They do all have insect-repelling action, though, and you can still use these in your own homemade repellents to create your own mixture.
- Tea tree
Make Your Own
If you’d like to make your own insect repellant using natural oils, you have a couple of options:
Dilute about 10 drops of your main oil (and a few drops of any other desired oils) in four ounces of witch hazel in a spray bottle and spray on skin and/or clothes. You can also add distilled water to the mix if desired.
Mix about 10 drops in the same amount of carrier oil, such as soybean (for added protection), sunflower, apricot kernel, or coconut.
Keep in mind that adding vanillin may help to extend the lasting power of your homemade solution.
Do you make your own insect repellents? How do they work for you?
Centers for Disease Control and Prevention – Zika virus disease in the United States, 2015–2016
EWG – EWG’S Guide to Bug Repellents in the Age of Zika
EWG – EWG’s Advice for Avoiding Bug Bites
Children MD – Do natural bug repellents work?
PubMed – Repellency of IR3535, KBR3023, para-menthane-3,8-diol, and deet to black salt marsh mosquitoes (Diptera: Culicidae) in the Everglades National Park.
NBCI – Plant-based insect repellents: a review of their efficacy, development and testing
National Pesticide Information Center – Oil of Citronella, General Fact Sheet
Medical Daily – Is Citronella Grass Your Best Bet For A Natural Mosquito Repellent This Summer?
PubMed – Effectiveness of citronella preparations in preventing mosquito bites: systematic review of controlled laboratory experimental studies.
Science Daily – Catnip Repels Mosquitoes More Effectively Than DEET
PubMed – Adult repellency and larvicidal activity of five plant essential oils against mosquitoes.
PubMed – Repellent activity of catmint, Nepeta cataria, and iridoid nepetalactone isomers against Afro-tropical mosquitoes, ixodid ticks and red poultry mites.
Discover Neem – Neem Natural Mosquito Repellent
NBCI – Toxicity of a plant based mosquito repellent/killer
PubMed – Laboratory evaluation of mosquito repellents against Aedes albopictus, Culex nigripalpus, and Ochierotatus triseriatus (Diptera: Culicidae).
PubMed – Comparative efficacy of insect repellents against mosquito bites.
PubMed – Efficacy of herbal essential oils as insecticide against Aedes aegypti (Linn.), Culex quinquefasciatus (Say) and Anopheles dirus (Peyton and Harrison).
PubMed – Bioactivity of cedarwood oil and cedrol against arthropod pests.
Wiley Online Library – Essential oils of Cupressus funebris, Juniperus communis, and J. chinensis (Cupressaceae) as repellents against ticks (Acari: Ixodidae) and mosquitoes (Diptera: Culicidae) and as toxicants against mosquitoes
PubMed – Use of novel compounds for pest control: insecticidal and acaricidal activity of essential oil components from heartwood of Alaska yellow cedar.
Annmarie Skin Care