The Mosquito Repellent Guide:
The World Health Organization has declared the Zika virus an international public health emergency due to its relation to birth defects. Dengue is also a concern in the Gulf Coast states of Florida and Texas as well as Hawaii for its role in increasing chronic kidney disease. The U.S. Virgin Islands, Puerto Rico, and Florida have each seen chikungunya blamed for causing debilitating joint pain. Throughout the U.S., West Nile contributes to neurological problems. Each one of these ailments is transferred to humans by the bite of a mosquito.
Although a dengue vaccine was recently approved in Mexico, there are no vaccines for any of these mosquito-borne viruses in the United States. Prevention is the key to staying healthy. Zika virus prevention means avoiding areas where the virus is spreading. Most cases of Zika in the continental United States come from traveling abroad, but areas of Florida are experiencing cases contracted directly by contact with mosquitos. The U.S. already has plenty of these disease carrying mosquito residents.
The biggest threat in areas of the United States is in the South, and in particular, the humid climate of the Southeast. Aedes aegypti, the mosquito responsible for dengue, chikungunya, and Zika, lives in this region, along with Central and South America, Africa, Australia and South Asia. The Aedes albopictus mosquito can also transmit these viruses and is more common throughout the United States but is less of a threat because it lives in more remote areas and does not prefer human blood. The Culex mosquitoes, the carriers of West Nile virus, are found everywhere in the United States.
The mosquitoes that spread Zika are usually not found in mountainous regions above 6,500 feet (2,000 meters) and these areas are considered low risk.
Multiple strategies work against mosquito bites. Wearing loose fitting long-sleeved pants and shirts that are both light in weight and color helps, so does wearing clothing treated with permethrin, but applying mosquito repellents to your exposed skin is probably the best. Combinations of these methods will increase your protection too.
- Look for insect repellents registered with the Environmental Protection Agency (EPA) containing DEET, Picaridin, para-menthane-diol (PMD), oil of lemon eucalyptus (OLE), or IR3535.
- Use permethrin-treated clothing like shirts, pants, and hats as well as gear like tents and nets.
- Treat clothing with repellent yourself.
- Make sure your accommodations have screened-in areas or air-conditioned rooms whenever possible or use a mosquito bed net whether you are inside or outdoors. Treated bed nets are available too.
- Use nets or fans over outdoor eating areas and porches
- Mosquito netting can be used to protect babies under 2 months old in carriers, strollers, or cribs.
- Dump out any containers of standing water around your residence.
Mosquitos are a fact of life. They exist in our environment and take advantage of warm weather. While we worry more during the summer months, many areas of the U.S., as well as other countries, experience mild winter weather and mosquitos are active at temperatures beginning at 50 or 60 degrees. This means, depending on where you live or travel, you need to be vigilant throughout other seasons as well. These pests are not only found in tropical forests and family campgrounds but gravitate to our homes in cities and towns.
This growing concern prompted Consumer Reports to conduct a test on popular repellents and release the results used to rate mosquito repellent effectiveness. These tests showed that some repellents work much better than others at protecting against mosquitos including those that transmit the more recent threat of Zika. The products tested containing ingredients like DEET, Picaridin, and oil of lemon eucalyptus were at the top of the list and those with chemicals called IR3535 and 2-Undecanone were shown to be less effective. Plant oils including cedar, citronella, geraniol, lemongrass, and rosemary were also tested and were shown to protect the least.
The Top 5:
- Sawyer Fisherman’s Formula, containing 20 percent Picaridin and lasting eight hours
- Natrapel 8 Hour, also with 20 percent Picaridin
- Off! Deepwoods VIII, using 25 percent DEET for eight full hours
- Ben’s 30% DEET Tick & Insect Wilderness Formula deterred mosquitos for 7.5 hours
- Repel Lemon Eucalyptus, with 30 percent lemon eucalyptus, was effective for 7 hours.
The Sawyer product can also deter mosquitoes and deer ticks, responsible for West Nile and Lyme diseases, for the same amount of time.
The IR3535 products containing 2-Undecananone did not make the list and neither did repellents with as little as seven percent DEET or under 20 percent Picaridin.
The 10 other products that Consumer Reports tested were only effective protection for up to three hours, with many lasting only a half hour. These lower dose solutions include:
- Repel Scented Family contains 15 percent DEET and comes as an aerosol spray
- Coleman SkinSmart 10 percent Picaridin
- Cutter Skinsations 7 percent DEET
- HOMS Bite Blocker BioUD Mini Trigger 7.75% 2-Undecanone
Based on the Consumer Reports study, repellents containing either DEET or Picaridin are most effective and continually show the best protection against bites and are proven to be safe to use even on children over the age of three months. Whether they repel or just confuse mosquitos, they stop the biting when used as directed on the label.
These products are available in aerosol sprays, pump sprays, roll-ons, gels, lotions, and wipes. The active ingredients in each are the same. Pick the one that you are most comfortable using to ensure you get good coverage on exposed skin. Be careful with aerosols as they can be inhaled or irritate the eyes. Put sprays on your hands and rub onto skin for better control of coverage and ensure you avoid getting repellent in your eyes, cuts, or abrasions. This is also recommended when applying repellent to children.
High Dose or Heavy Duty Repellents
The highest-dose repellent contains 80% DEET and laboratory studies show it protects for over ten hours from biting mosquitoes. Why are these repellents not on the Consumer Reports list?
The strength of the formulation determines the length of time you are protected against mosquito bites; not how many mosquitoes are kept away.
- 10 percent DEET-based repellent provides about 2 hours of protection.
- 20 percent may provide nearly 4 hours of protection.
When choosing a repellent, think about the length of time you will need protection and how often you want to reapply. A lower dose of repellent is fine for short periods of exposure and provides protection during that period equivalent to a higher dose or tropical strength products.
The low dose will need to be reapplied if you need longer protection while the “high dose” is designed to last more hours. DEET and Picaridin-based repellents both work this way. Common sense determines the level of compromises between comfort and protection depending on your location and risk for infection.
The repellent must be applied evenly on all exposed skin. Mosquitoes can find any untreated place to bite. In the case of the mosquitos that spread Zika, dengue and chikungunya viruses, apply liberally around the lower legs and feet where they are known to bite most often. Reapply after swimming and sweating. Applying repellents under clothing is pointless and can inhibit evaporation of the product as well as build up on clothing.
Some people insist on avoiding chemicals like DEET to use a natural, plant-based repellent despite DEET’s EPA safety approval. Natural products provide shorter periods of protection and can cause skin irritation. These plant-based repellents can offer some protection against biting pests, but should not be relied on in Zika zones or other mosquito-borne disease outbreak areas.
Many health authorities recommend para-Menthane-3,8-diol (PMD), also referred to as “oil of lemon eucalyptus”. It is a by-product of the distillation process of Corymbia citriodora – a eucalyptus tree found in Australia. It will repel many types of biting insects and is considered safe for pregnant women.
Extracts from many different plants are known to naturally repel mosquitoes in plant-based topical repellents on their own or blended combinations of citronella, eucalyptus, lavender, tea-tree, or catmint oils.
Many of these can only be effective for about 20 minutes to one hour which is minimal in comparison to the extent of protection from DEET or Picaridin-based repellents. If you are outside for only a short time, it might not be an issue. However, taking a long hike through local wetlands or spending the late afternoon in the garden will require you to reapply natural repellents three to four times as often as low dose DEET-based products. In recent studies, botanical products failed nearly immediately against the Aedes mosquitoes.
Most plant-oil products are exempt from EPA testing because they are considered to be a minimum health risk. The EPA requires these products to provide a number on package labels when it is registered and approved. Even those products registered are usually not advised for children under 12 months old.
Other Repellent Options
Purchasing permethrin-treated clothing including long sleeve shirts and pants along with hats and head nets works well in areas with high mosquito populations. You will want to apply the best possible topical repellent to any exposed skin to be fully protected.
To be effective, spraying repellent on clothing yourself requires applying it to fabric like you would to your skin, making certain they are fully covered. A thin cover may be enough for short periods of protection. Again, you will need to apply repellent to exposed skin as well.
Wristbands contain an essential oil to help reduce the number of mosquitos that may bite close to the band, and very little protection anywhere else. They are not an effective alternative as topical repellents.
Mosquito coils and sticks contain plant-based repellents such as citronella. They help reduce the number of biting mosquitoes, but will not completely protect the way a topical DEET-based repellent will.
Hiring exterminators or investing in misting systems to spray pesticides outside the home is a temporary fix, but only for Culex mosquitos, which remain outside. Aedes, are often found seeking shade indoors. Regardless, the adult mosquitos are killed, but new mosquitoes will quickly repopulate inside your house. Pesticides also need to reach the standing water and areas around homes where mosquitoes breed.
Pregnant Women and Children
Currently, the CDC discourages pregnant women from traveling to countries where Zika has become a problem since the risk specifically involves birth defects. This includes Latin America and the Caribbean, Puerto Rico, and the U.S. Virgin Islands.
Remember that Zika mosquitoes are usually not in mountainous regions at heights over 6,500 feet. Locations at this elevation are considered a very low risk for getting Zika.
Most health authorities and government agencies see no need to provide warnings on the use of insect repellents by pregnant women. Recent studies using mosquito repellent in the second or third trimester of pregnancy show no signs of negative effects to skin, brain, nerves, or digestive functions in women or their infants for up to a year after birth. Breastfeeding women can also use all EPA-registered insect repellents as long as they follow the directions on the product label.
There is more information reported by the CDC for pregnant travelers on Zika risk and prevention. Also, advice from the CDC is available if you are planning to travel while pregnant. Consulting your doctor is always recommended.
Tips for Mom
Avoiding wetlands at dawn and dusk will ensure you are missing the time and place where mosquitoes are most active.
Wearing light-colored long-sleeved shirts and pants will attract fewer insects. Loose-fitting clothing makes it harder for mosquitos to reach the skin so avoid wearing your yoga pants and leggings. It is safe for you to use clothing treated with an insecticide like permethrin.
Find out if you are traveling to an area where the mosquitos have become resistant to permethrin – such as Puerto Rico. You can treat your own clothing with alternatives like DEET and Picaridin products. You may want to have someone help you with the application process to avoid unnecessary additional exposure to the chemicals.
For exposed skin, choose the lowest effective dose of DEET or Picaridin in the repellent and reapply as needed according to the number of hours of protection the dose provides.
Para-Menthane-3,8-diol (PMD), also deters biting insects and studies suggest it can be used safely during pregnancy.
Most repellents, including DEET, are able to be applied to children over the age of 2 months. Do not spray repellent directly onto a child’s face. Adults should spray it on their hands and then spread it on the child’s skin. Use mosquito nets to protect infants under 2 months old.
Tips for Children:
- Do not apply repellent to the child’s hands because hands may end up in their mouths.
- Store bug repellent in a place away from young children who may accidentally ingest it.
- Choose a repellent with a dosage closest to the time your children will be outdoors: Picaridin (20 percent), IR3535 (20 percent), DEET (7-30 percent).
- Clean repellent from the skin at the end of the day.
- Oil of Lemon Eucalyptus (PMD) for children less than 3 years of age.
- Over 30 percent DEET when you are able to reapply as needed. (unless you have prolonged exposure to a disease prone area)
- Chemical repellent on children under 2 months and continue to avoid until age 6 months.
- Aerosol sprays that create a risk of inhalation and exposure to the eyes and nose.
- Pre-mixed repellent and sunscreen since the SPF must be applied every two hours and leads to overexposure to the chemicals.
- Outdoor insecticides designed to “fog” large areas. They contain more toxic ingredients than repellents applied to the skin.
- Repellent candles that emit fumes and can prompt respiratory problems.
- Bug zappers and treated wristbands.
Before Leaving on Vacation
Pack enough repellent for your entire vacation if possible. Certain products may not be available or have gone through the process of registration with the EPA or other government regulation at your destination. With recent health threats, some of the best mosquito repellents could be sold out when you arrive.
If you’re traveling to regions experiencing outbreaks of dengue, chikungunya, West Nile, and Zika virus, you will not necessarily be swarmed by mosquitoes like when visiting the tropics and coastal wetlands. There may be only a few around, but it only takes one to transmit a disease.
Centers for Disease Control and Prevention, Zika, http://www.cdc.gov/zika/healtheffects/gbs-qa.html
Centers for Disease Control and Prevention, Zika Areas http://wwwnc.cdc.gov/travel/page/travelers-vfr-chikungunya-dengue-zika
Centers for Disease Control and Prevention, Zika Travel Information, http://wwwnc.cdc.gov/travel/page/zika-travel-information
Consumer Reports, Insect Repellents, http://www.consumerreports.org/products/insect-repellent/ratings-overview/
Epstein, S., 2016. The 5 Most Effective Mosquito Repellents: Consumer Reports, Today Health and Wellness, http://www.today.com/health/5-mosquito-repellents-best-protect-against-zika-virus-consumer-reports-t72761
EWGs Guide to Repellents in the Age of Zika, Dos and Don’ts for avoiding Bug Bites, http://www.ewg.org/research/ewgs-guide-bug-repellents/ewgs-dos-and-donts-avoiding-bug-bites
Sharp, R., 100% DEET: Good Protection or Bad Idea, 2013. http://www.ewg.org/enviroblog/2013/07/100-deet-good-bug-protection-or-bad-idea
Storrs, C., 2016. CNN Health, Where the Zika Mosquitoes Are Hiding and How to Stop Them, http://www.cnn.com/2016/01/21/health/preventing-mosquito-borne-viruses-zika-dengue-west-nile/
Webb, C., 2015. The Conversation, Chemical or Natural: Which is the Best Way to Repel Mozzies? https://theconversation.com/chemical-or-natural-whats-the-best-way-to-repel-mozzies-36879
- C., and Russell, R., 2009. Insect Repellents and Sunscreen: Implications for Personal Protection Strategies Against Mosquito-Borne Disease, http://onlinelibrary.wiley.com/doi/10.1111/j.1753-6405.2009.00435.