EWG’s guide to bug repellents

Updated May 30, 2024.

Latin America is facing its worst outbreak of dengue fever, and many other places around the world are seeing cases soar – but a safe bug repellent can help protect against this and other diseases from pests.

EWG’s just-updated Guide to Bug Repellents offers crucial tips on what to look for when buying these products, and how to most effectively reduce the risk of getting infected by dengue fever and other diseases that might otherwise easily spread from insects to humans.

Increases in dengue fever around the world highlight the problem. In just the first five months of 2024, Latin America’s recorded cases are 238 percent higher than they were by this time last year. 

Other areas are coming up against an uptick, too. Puerto Rico declared a public health emergency in late March, after more than 400 people were hospitalized with the illness.

Dengue fever, also called “break-bone fever” due to the intense body pain it can cause, is a viral infection that spreads from mosquitoes to humans. Many people who contract the virus are asymptomatic, but those with symptoms – one in four – )commonly experience a high fever, headache, body aches, nausea and a rash. 

Most people recover in a couple of weeks, but about one in 20 people develops severe dengue, which can be fatal. The more often a person contracts it, the higher risk for a severe outcome.

The warming climate has created the perfect environment for Aedes aegypti, the mosquitos that carry dengue fever, to expand their range. These insects are now regularly found in the southern United States and recently have been spotted as far north as Washington, D.C., and the Bay Area.

Rising disease rates

These dengue fever cases appear amid rising rates of other diseases transmitted by ticks and insects, which can cause serious health problems, even death. The CDC warns that pest-borne diseases are “a large and growing public health problem in the United States.”

Tick-borne diseases, primarily Lyme disease, contribute significantly to this increase. According to the health insurance data nonprofit FAIR Health, Lyme disease diagnoses surged by 357 percent in rural areas and 65 percent in urban areas over the past 15 years.

The rise in cases is compounded by a surge in heat waves and wildfires taking place at the same time. The rise in cases point to tangible health problems caused by the climate crisis. Experts predict bites and infections will keep rising because of a warming climate, which expands the habitat of species such as ticks and mosquitoes. 

People need greater protection from the risk of diseases carried by pests and EWG’s guide aims to help them learn how to find a bug repellent that works and is safe to use.

Three key active ingredients

EWG researchers have analyzed the science behind bug repellants and found that with proper application and precaution, repellents that contain three key active ingredients can effectively reduce a person’s risk from life-altering diseases. 

They are:

• DEET (at less than 30 percent) [Learn more].
• IR3535 (at 20 percent) [Learn more].
• Picaridin [Learn more].

The Environmental Protection Agency regulates insect repellents and requires companies to submit data to verify their claims of repellency. When a company registers a bug repellent, it must provide the EPA with technical information that shows the chemical is effective against mosquitoes, ticks or both. The EPA must approve any marketing claims that assert the repellent works for a particular length of time. Consumers should use an EPA-registered repellent. 

When vector-borne disease is a concern, start with the repellents that have been shown in tests to be the most efficient in a range of situations.

If you can’t find any bug repellents that have the active ingredients DEET, IR3535 or Picaridin, then some other effective ingredient options are:

• Oil of Lemon Eucalyptus and its synthetic derivative PMD [Learn more].

These repellents offer a high level of protection from a variety of biting insects and ticks, have good safety profiles, and are registered with the EPA, so their manufacturers must provide data on both efficacy and toxicity. 

If a product is not working for you or your family, we recommend trying one with a different active ingredient. The EPA maintains an online repellent search tool to help you find products that it has reviewed.

DEET proves effective

DEET has a long history of use and is very effective in reducing bites. In the 60 years DEET has been available to the public, few cases of toxicity have been reported. 

Concerns have been raised about DEET’s potential to be neurotoxic to children but follow-up studies have not linked DEET to neurotoxicity. 

A 2003 report found no evidence of an increased risk of adverse toxic effects in young children. A 2017 report also found it unlikely that DEET causes neurotoxicity. A 2020 study by researchers at the University of Florida found that DEET exposure is likely safe for human use, showing no increased risk of negative health impacts.

Before setting off on your adventures, check the CDC’s travel site for up-to-date information on bug-borne diseases.

What to look for in bug repellent

You should research the diseases carried by mosquitoes, and by other insects and ticks, where you plan to spend time outside. The repellent you might choose for a backpacking trip in Colorado could be different from the one that might suffice for a picnic on an East Coast beach.

Based on testing data, we recommend starting with these three active ingredients for protection from a variety of biting insects and ticks:

• Picaridin [Learn more]
• DEET (at less than 30 percent) [Learn more]
• IR3535 (at 20 percent) [Learn more]

The two repellents below may also be good options and should provide similar protection but, perhaps, for shorter durations:

• Oil of Lemon Eucalyptus and its synthetic derivative PMD [Learn more]
• 2-Undecanone [Learn more]

But beware when using any of these repellent chemicals: You must follow the guidelines on product labels to avoid overexposure. These are strong chemicals that should not be used on infants under 6 months old.

If you are hesitant to try a new bug repellent, start using it in your backyard, neighborhood and places you go regularly. If one product fails to deter biting bugs as you had hoped, next time try a different formulation with a higher percentage of the repellent chemical, or a product with another active ingredient.

EWG does not recommend products that combine repellent and sun protection.

What to do before you grab the repellent

Give bugs a smaller target. Cover up with light-colored clothing. In areas with a lot of bugs, wear long-sleeve shirts with high collars and bandanas. When walking in tall grass or brush, tuck pants into socks to keep ticks and chiggers off your body. Use nets and/or fans over outdoor eating areas, and place nets over strollers and baby carriers. If your kids are going to camp, send them with mosquito netting for their bunks.

Get rid of mosquito breeding grounds. Drain standing water around your home. If you live in a place with a high tick concentration, make a wood chip barrier between your yard and wooded areas, mow the lawn, clean up brush regularly and follow the CDC’s guidelines for reducing your yard’s tick population.

Know your enemy. If you are in a place that presents few risks for pest-borne diseases and you don’t mind getting a few bug bites, your choice of repellent may not be that critical. On the other hand, if you need to protect yourself from Lyme disease, West Nile virus, Zika, dengue fever or other serious mosquito- and tick-transmitted diseases, your repellent and other preventive actions are serious decisions. It is vital that you research the common pest-borne diseases in your area – or where you are headed – so that you can match your choices to your risks.

Lyme disease cases are highly concentrated in 14 Northeastern and Mid-Atlantic states, from Virginia to Maine, and in the upper Midwest, mostly in Wisconsin and Minnesota. You are most likely to contract Lyme disease between late April and August.

West Nile cases have been found in almost every state, with the most cases reported in 2017 in Arizona, Texas, California and Illinois. According to the CDC, infections from mosquitoes carrying West Nile virus occur primarily in the summer months, peaking in August.

Much more information is available from the CDC and the World Health Organization.

For adults

I WANT TO PROTECT MYSELF AGAINST DENGUE FEVER

Choose a repellent with picaridin at a 20 percent concentration, or DEET at a 20 to 30 percent concentration. Choose a concentration based on the amount of time you plan to spend outdoors.

Other things to consider:

• No repellent is 100 percent effective, so take extra precautions to avoid mosquito bites.
• Cover up with pants and long-sleeve shirts when possible, especially if you need protection from both the sun and mosquitoes.
• Wash your hands after applying repellent and wash repellent-coated skin at the end of the day.

I WANT TO PROTECT MYSELF AGAINST LYME DISEASE

Choose a repellent with picaridin at a 20 percent concentration, DEET at a 20 to 30 percent concentration, IR3535 at a 20 percent concentration, or Oil of Lemon Eucalyptus at a 30 to 40 percent concentration.

Other things to consider:

• No repellent is 100 percent effective, so take extra precautions to avoid tick bites.
• Cover up with pants, socks and shoes and long-sleeve shirts, especially when venturing into heavy brush with likely tick infestations. Consider permethrin-treated clothing.
• Check out the CDC's Lyme Disease maps to find out if you are in a high-risk area.
• Check for ticks thoroughly every night and remove ticks properly.
• Natural lemon eucalyptus oil is not the same as Oil of Lemon Eucalyptus.
• Wash your hands after applying repellent and wash repellent-coated skin at the end of the day.

I WANT TO PROTECT MYSELF AGAINST ZIKA VIRUS

Choose a repellent with picaridin at a 20 percent concentration or DEET at a 20 to 30 percent concentration. Choose a concentration based on the amount of time you plan to spend outdoors.

Other things to consider:

• No repellent is 100 percent effective, so take extra precautions to avoid mosquito bites.
• Cover up with pants and long-sleeve shirts when possible, especially if you need protection from both the sun and mosquitoes.
• Wash your hands after applying repellent and wash repellent-coated skin at the end of the day.

I WANT TO PROTECT MYSELF AGAINST WEST NILE VIRUS

Choose a repellent with picaridin at a 10-20 percent concentration, DEET at a 7 to 30 percent concentration, or IR3535 at a 20 percent concentration. You may also consider a product with Oil of Lemon Eucalyptus at 30 to 40 percent, PMD at 10 percent, or 2-undecanone. Choose a concentration based on the amount of time you plan to spend outdoors.

Other things to consider:

• Check out the CDC's West Nile virus maps to find out if you are in a high-risk area.
• No repellent is 100 percent effective, so take extra precautions to avoid mosquito bites.
• Cover up with pants and long-sleeve shirts when possible, especially when venturing into mosquito-infested areas.
• PMD has a shorter protection time than other repellents. 
• Natural lemon eucalyptus oil is not the same as Oil of Lemon Eucalyptus.
• Wash your hands after applying repellent and wash repellent-coated skin at the end of the day.

I'M TRAVELING OUT OF THE COUNTRY

Choose a repellent with picaridin, DEET or IR3535. Choose a concentration based on the amount of time you plan to spend outdoors, and check with your doctor for other protective measures.

Other things to consider:

• Risks vary by country, so consult your physician and the CDC or the World Health Organization's traveler information sites about risks in places you plan to visit.
• Bug repellent alone may not protect you from malaria. Check with your doctor.

I NEED TO BE OUTDOORS FOR A SHORT TIME

Consider picaridin at a 5-10 percent concentration, DEET at a 7 to 10 percent concentration or PMD at a 10 percent concentration.  

Other things to consider:

• Wash your hands after applying repellent and wash repellent-coated skin at the end of the day.

I NEED BUG PROTECTION FOR THE ENTIRE DAY

Choose a repellent with picaridin at a 20 percent concentration or DEET at a time release 20 to 30 percent concentration.

Other things to consider:

• Daily use of DEET for prolonged periods may be inadvisable. Consult your doctor.
• Wash your hands after applying repellent and wash repellent-coated skin at the end of the day.

I HAVE SENSITIVE SKIN or ALLERGIES

Choose a repellent with: Your best bet may be picaridin at a 5 to 20 percent concentration because it is less likely to irritate skin and trigger allergies. People react differently, so you may want to try other options to find out what works for you.

Other things to consider:

• Try repellents on a small patch of exposed skin before slathering it all over.
• DEET and IR3535 may cause eye irritation, and DEET may cause skin irritation.
• Oil of Lemon Eucalyptus may cause allergic skin reactions.
• Wash your hands after applying repellent and wash repellent-coated skin at the end of the day.

BUG-BORNE DISEASES ARE NOT PREVALENT WHERE I LIVE

Choose a repellent with picaridin, DEET, IR3535, Oil of Lemon Eucalyptus, PMD or 2-undecanone. Choose a concentration based on the amount of time you plan to spend outdoors. 

Other things to consider:

• Natural lemon eucalyptus oil is not the same as Oil of Lemon Eucalyptus.
• Wash your hands after applying repellent and wash repellent-coated skin at the end of the day.

I'M GOING CAMPING WHERE MOSQUITOES ARE RAMPANT

Choose a repellent with picaridin at a 10 to 20 percent concentration, DEET at a 7 to 30 percent concentration, or IR3535 at a 20 percent concentration. You may also consider a product with Oil of Lemon Eucalyptus at 30 to 40 percent, PMD at 10 percent, or 2-undecanone.

Other things to consider:

• No repellent is 100 percent effective. Cover up with pants and long-sleeve shirts when possible.
• Natural lemon eucalyptus oil is not the same as Oil of Lemon Eucalyptus.
• Wash your hands after applying repellent and wash repellent-coated skin at the end of the day.

For kids

I WANT TO PROTECT MY KIDS AGAINST LYME DISEASE

Choose a repellent with picaridin at a 20 percent concentration, IR3535 at a 20 percent concentration, DEET (see note for concentrations), or Oil of Lemon Eucalyptus at a 30 to 40 percent concentration, unless your child is under 3 years old.

Other things to consider:

• No repellent is 100 percent effective, so take extra precautions to avoid tick bites.
• Dress your kids in pants, socks and shoes, and long-sleeve shirts, especially when they are venturing into heavy brush with likely tick infestations. Also consider permethrin-treated clothing.
• Health agencies offer conflicting advice about the DEET concentration safe for children. The CDC’s 2016 recommendation suggested DEET with maximum concentrations of 20 to 30 percent for children's protection from Lyme disease borne by ticks.6 Health Canada recommends DEET with concentrations no greater than 5 to 10 percent for children.7 But this weaker concentration may not offer a strong defense against ticks bearing Lyme disease.
• Check your kids thoroughly for ticks every night and remove ticks properly.
• The CDC advises not to use Oil of Lemon Eucalyptus or PMD on children under 3 years old.
• Natural lemon eucalyptus oil is not the same as Oil of Lemon Eucalyptus.
• When using repellent on a child, apply it to your own hands and then rub them on the child. Avoid the child's eyes and mouth. Use repellent sparingly around ears. Do not apply repellent to the child's hands because children may put their hands in their mouths.
• Wash hands after applying repellent and wash repellent-coated skin at the end of the day.
• Keep bottles of bug repellent away from young children to reduce chances of accidental swallowing.

I WANT TO PROTECT MY KIDS FROM ZIKA VIRUS

Choose a repellent with picaridin at a 20 percent concentration or DEET at a 7 to 30 percent concentration. Choose a concentration based on the amount of time your kids will be outdoors.

Other things to consider:

• Cover kids’ skin with pants and long-sleeve shirts when possible, especially if they need protection from both sun and mosquitoes.
• Daily use of DEET for prolonged periods may be inadvisable for children. Consult your doctor.
• When using repellent on a child, apply it to your own hands and then rub them on the child. Avoid the child’s eyes and mouth. Use repellent sparingly around ears. Do not apply repellent to the child’s hands because children may put their hands in their mouths.
• Keep bottles of bug repellent away from young children to reduce the chances of accidental swallowing.
• Wash repellent-coated skin at the end of the day.

I WANT TO PROTECT MY BABY FROM BUG BITES

Do not use bug repellents on infants under 6 months old.

Other things to consider:

• Use fine netting over strollers and baby carriers.

I WANT TO PROTECT MY KIDS AGAINST WEST NILE VIRUS

Choose a repellent with picaridin at a 10 to 20 percent concentration, DEET at a 7 to 10 percent concentration, or IR3535 at a 20 percent concentration. You may also consider Oil of Lemon Eucalyptus at a 30 to 40 percent concentration or PMD at a 10 percent concentration – unless your child is under 3 years old (see note) – or 2-undecanone. Choose a concentration based on the amount of time your kid will spend outdoors.

Other things to consider:

• Check out the CDC’s West Nile virus maps to find out if you are in a high-risk area.
• No repellent is 100 percent effective, so take extra precautions to avoid mosquito bites.
• Cover up with pants and long-sleeve shirts when possible, especially if venturing into mosquito-infested areas.
• The CDC advises not to use Oil of Lemon Eucalyptus or PMD on children under 3 years old.
• Natural lemon eucalyptus oil is not the same as Oil of Lemon Eucalyptus.
• When using repellent on a child, apply it to your own hands and then rub them on the child. Avoid the child’s eyes and mouth. Use repellent sparingly around ears. Do not apply repellent to the child’s hands because children may put their hands in their mouths.
• Wash hands after applying repellent and wash repellent-coated skin at the end of the day.
• Keep bottles of bug repellent away from young children to reduce chances of accidental swallowing.

MY KID HAS SENSITIVE SKIN or ALLERGIES

Your best bet may be picaridin at a 5 to 20 percent concentration because it is less likely to irritate skin and trigger allergies. People react differently, so you may want to try other options to see what works for your child.

Other things to consider:

• Try repellents on a small patch of exposed skin before slathering them all over.
• DEET and IR3535 may cause eye irritation. DEET may cause skin irritation.
• Oil of Lemon Eucalyptus may cause allergic skin reactions.
• The CDC advises not to use Oil of Lemon Eucalyptus or PMD on children under 3 years old.
• When using repellent on a child, apply it to your own hands and then rub them on the child. Avoid the child’s eyes and mouth. Use repellent sparingly around ears. Do not apply repellent to the child’s hands because children may put their hands in their mouths.
• Wash hands after applying repellent and wash repellent-coated skin at the end of the day.
• Keep bottles of bug repellent away from young children to reduce chances of accidental swallowing.

I'M SENDING MY KIDS TO CAMP

Choose a repellent with: Consider picaridin at a 5 to 20 percent concentration, DEET at a 7 to 10 percent concentration, or IR3535 at a 20 percent concentration. Choose a concentration based on the amount of time your kid will spend outdoors.  

Other things to consider:

• Send kids to camp with netting for their bunks.
• Picaridin is less likely to irritate eyes and skin, and may be a good choice.
• Natural lemon eucalyptus oil is not the same as Oil of Lemon Eucalyptus.
• Tell your kids to wash their hands after applying repellent and to wash repellent-coated skin at the end of the day.

BUG BORNE DISEASES ARE NOT PREVALENT WHERE WE LIVE

Choose a repellent with picaridin at a 5 to 10 percent concentration, DEET at a 7 to 10 percent concentration, or IR3535 at a 20 percent concentration. You may also consider Oil of Lemon Eucalyptus at 30 to 40 percent, unless your child is under 3 years old (see note); PMD at 10 percent; or 2-undecanone. Base the concentration that you choose on the amount of time your kid will spend outdoors.  

Other things to consider:

• If disease-bearing bugs aren't common and bites are infrequent, consider going without repellent.
• Picaridin is less likely to irritate eyes and skin, and may be a good choice.
• The CDC advises not to use Oil of Lemon Eucalyptus or PMD on children under 3 years old.
• Natural lemon eucalyptus oil is not the same as Oil of Lemon Eucalyptus.
• When using repellent on a child, apply it to your own hands and then rub them on the child. Avoid the child's eyes and mouth. Use repellent sparingly around ears. Do not apply repellent to the child's hands because children may put their hands in their mouths.
• Wash hands after applying repellent and wash repellent-coated skin at the end of the day.
• Keep bottles of bug repellent away from young children to reduce chances of accidental swallowing.

For pregnant women

I'M PREGNANT AND NEED ZIKA PROTECTION

Choose a repellent with Picaridin at a 20 percent concentration, or DEET at a 20 to 30 percent concentration.

Scientists have generally found bug repellents to be safe for pregnant women and their unborn children. The risk of Zika infection is far more serious than side effects of the chemical repellents, provided you use them as directed.

Other things to consider:

• Try to avoid travel to places where active transmission of Zika is possible.
• Read the current CDC recommendations.
• No repellent is 100 percent effective, so take extra precautions to avoid mosquito bites.

I'M PREGNANT AND NEED LYME DISEASE PROTECTION

.As a first line of defense, try to avoid tick bites by covering up with pants, socks, shoes and long sleeves. Consider using picaridin at a 20 percent concentration, DEET at a 20 to 30 percent concentration, or IR3535 at a 20 percent concentration for extra protection.

Other things to consider:

• No repellent is 100 percent effective, so take extra precautions to avoid tick bites.
• Check out the CDC's Lyme disease maps to find out if you are in a high-risk area.
• Check for ticks thoroughly every night and remove ticks properly.
• The CDC advises not to use Oil of Lemon Eucalyptus or PMD on very young children, so avoid it while pregnant.
• Wash your hands after applying repellent and wash repellent-coated skin at the end of the day.
• Avoid excessive use of any repellent during pregnancy

I'M PREGNANT AND NEED WEST NILE VIRUS PROTECTION

As a first line of defense, try to avoid mosquito bites by covering up with pants and long sleeves. Also consider using a product with any of the EPA-approved active ingredients: picaridin at a 10 to 20 percent concentration, DEET at a 7 to 30 percent concentration, or IR3535 at a 20 percent concentration. Base the concentration you choose on the amount of time you plan to spend outdoors. Use weaker concentrations and reapply as necessary.

Other things to consider:

• No repellent is 100 percent effective, so take extra precautions to avoid mosquito bites.
• Check out the CDC's West Nile Virus maps to find out if you are in a high-risk area.
• The CDC advises not to use Oil of Lemon Eucalyptus or PMD on very young children, so avoid it while pregnant.
• Wash hands after applying repellent and wash repellent-coated skin when you come indoors.
• Avoid excessive use of any repellent during pregnancy.

I'M PREGNANT AND WILL BE OUTDOORS FOR A SHORT TIME

As a first line of defense, cover up with pants and long sleeves. Consider using picaridin at a 5 to 10 percent concentration or DEET at a 7 to 10 percent concentration. Use weaker concentrations and reapply as necessary.

Other things to consider:

• Take precautions to avoid both bug bites and excessive repellent exposure during pregnancy.
• CDC advises not to use Oil of Lemon Eucalyptus or PMD on very young children, so avoid it while pregnant.
• Wash hands after applying repellent and wash repellent-coated skin at the end of the day.

I'M PREGNANT AND NEED ALL-DAY BUG PROTECTION

As a first line of defense, cover up with pants and long sleeves. Also consider using picaridin at a 5 to 10 percent concentration or DEET at a 7 to 10 percent concentration. Use weaker concentrations and reapplying as necessary.

Other things to consider:

• Take precautions to avoid both bug bites and excessive repellent exposure during pregnancy.
• Daily use of DEET for prolonged periods may be inadvisable. Consult your doctor.
• Wash hands after applying repellent and wash repellent-coated skin at the end of the day.

I'M PREGNANT AND HAVE SENSITIVE SKIN or ALLERGIES

As a first line of defense, cover up with pants and long sleeves. Your best repellent choice may be picaridin at a 5 to 10 percent concentration because it has the fewest irritation and allergy concerns. People's bodies react differently, so you may want to try other options to see what works best for you. Use lower concentrations and reapply as necessary.

Other things to consider:

• Take precautions to avoid both bug bites and excessive repellent exposure during pregnancy.
• Try repellents on a small patch of exposed skin before slathering it all over.
• DEET and IR3535 may cause eye irritation, and DEET may cause skin irritation.
• The CDC advises not to use Oil of Lemon Eucalyptus or PMD on very young children, so avoid it while pregnant. It may cause allergic skin reactions.
• Wash hands after applying repellent and wash repellent-coated skin at the end of the day.

BUG-BORNE DISEASES ARE RARE WHERE I LIVE

If the bugs aren't bad, consider forgoing repellent entirely. Otherwise, consider picaridin, DEET or IR3535. Base the concentration you choose on the amount of time you plan to spend outdoors, but use lower concentrations and reapply as necessary.

Other things to consider:

• Take precautions to avoid both bug bites and excessive repellent exposure during pregnancy.
• The CDC advises not to use Oil of Lemon Eucalyptus or PMD on very young children, so avoid it while pregnant.
• Wash hands after applying repellent and wash repellent-coated skin at the end of the day.

Do’s and don’ts for avoiding bug bites

Do:

• Wear pants, socks, shoes and long sleeve shirts, especially when venturing into heavy brush with likely bug infestations. Tuck pants into socks to protect the ankles.
• Take extra precautions to avoid bug bites if you are in a high-risk area for Lyme disease, West Nile virus, or other mosquito- and tick-borne illnesses.
• Use nets and/or fans over outdoor eating areas, and place nets over strollers and baby carriers.
• Read repellent labels to learn about safe usage and protection from bug species known to infest your area.
• Choose an EPA-registered repellent at the concentration rated for the amount of time you will be outdoors, but not longer. 
• Use products with the lowest effective concentration of repellent chemicals, particularly on children.
• Consult a physician if you are traveling out of the U.S. or need to use bug repellent daily for prolonged periods.
• Take extra care with kids. Keep repellents away from young children to reduce risk of accidental swallowing.
• Send kids to camp with netting for bunks.
• When using repellent on a child, apply it to your own hands and then rub them on your child. Avoid their eyes and mouths, and use repellent sparingly around their ears. Do not apply repellent to children's hands because they sometimes put their hands in their mouths.
• Use products in lotion, pump or towelette form.
• Try repellents on a small patch of exposed skin before slathering it all over.
• Check for ticks thoroughly after returning indoors and remove ticks properly.
• Wash clothing and repellent-coated skin when your kids come indoors or at the end of the day.
• Get rid of standing water where mosquitoes breed.
• Treat clothing containing with permethrin with caution. Wash treated clothing separately from other clothes.

Don’t use:

• Oil of Lemon Eucalyptus/PMD on children younger than 3 years old.
• More than 30 percent DEET on anyone.
• Any bug repellents on children under 6 months old.
• Outdoor “fogger” insecticides. They contain more toxic ingredients than repellents applied to skin.
• Repellent candles. They may not be effective. They emit fumes that could trigger respiratory problems.
• Aerosol sprays in pressurized containers. You’ll inhale chemicals, and you could get sprayed in the eyes.
• Repellent mixed with sunscreen. If you reapply the sunscreen every two hours, as advised, you will overexpose yourself to repellent.
• Bug zappers and treated wristbands.

Repellent chemicals

Picaridin

Picaridin, developed by Bayer AG in the 1980s and sold in the U.S. since 2005, has very low inhalation toxicity, is not known to irritate skin, and does not have a pungent odor like DEET.8 It evaporates from the skin more slowly than DEET or IR3535, and may repel bugs for longer periods. A review of reports to the National Poison Data System between 2000 and 2015 found only one moderate effect reported from the use of picaridin-containing products – the remaining cases were classified as having minor impacts, including ocular irritation or pain, vomiting or oral irritation.

In efficacy testing picaridin performs like DEET, appearing to repel a wide range of pests. A 2018 science review comparing the mosquito repellency of DEET with picaridin considered more than 140 field and laboratory studies and found no significant difference in performance. EPA registration data indicate that picaridin at a concentration of 20 percent is effective against mosquitoes and ticks for eight to 14 hours, and at a concentration of 10 percent it is effective for five to 12 hours.

Picaridin does not carry the same neurotoxicity concerns as DEET, but has not been used as extensively by people. Overall, EWG’s assessment is that picaridin is a good alternative to DEET with many of the same advantages and without the same disadvantages.

DEET

DEET, registered for public use in 1957, is the most common mosquito and tick repellent. It is rated as very effective in repelling a wide range of mosquitoes, ticks and other bugs. DEET has been used billions of times and is a reasonable, if imperfect, choice.

When used as directed, DEET is considered safe by many public health organizations, including the Environmental Protection Agency, the Centers for Disease Control and Prevention, the American Academy of Pediatrics and the World Health Organization.

In 1998, the EPA reviewed the first 40 years of public usage of DEET along with its known toxicity information, and concluded that “the normal use of DEET does not present a health concern to the general U.S. population.”13 And the agency found “no toxicologically significant effects in animal studies.”

When EWG started our research, we were particularly concerned about the potential downsides of DEET. We still are. We urge consumers to handle DEET with caution. It is known to irritate the eyes and in intense doses it may induce neurological damage. In very rare cases, DEET has been reported to impair the nervous system, with symptoms including seizures, tremors and slurred speech – this most often occurs after exposure to high concentrations of the chemical. In addition, DEET gives off a distinct odor, and can damage plastic, rubber and vinyl on clothing, backpacks, glasses, watches and cameras.

In 1998, after reviewing case reports of seizures, the EPA concluded that the rate of adverse reactions appeared to be very low – on the order of 1 per 100 million persons. The agency instructed manufacturers to provide additional instructions for minimizing overexposure to DEET. It authorized DEET for use by children, but banned marketing claims that DEET products are “safe for children.” The EPA said it had “no evidence that would lead [it] to believe that DEET is uniquely toxic to infants and/or children,” but it added that its personnel still had “concerns regarding these seizures, especially for children who are more susceptible to seizures in general and who receive a higher dose of DEET due to a greater surface area to body weight ratio.”

Laboratory studies conducted since the 1998 EPA review have suggested that intense DEET exposure can affect the nervous systems of rats.24,25 People who use DEET daily have reported suffering symptoms including rashes, dizziness, difficulty concentrating and headaches.

Still, after reviewing the evidence, EWG has concluded that DEET is generally safer than many people assume and remains a viable option for people in areas infested with disease-carrying pests. As rates of bug-borne illnesses rise, people need bug repellents that work well when it counts.

The EPA allows sales of repellents with up to 100 percent DEET, but increasing concentration does not increase efficacy. Longer protection times can be achieved by time-release products. We think it makes sense to follow Canadian government recommendations limiting DEET to 30 percent in any product, and using even weaker concentrations for young children. The Canadian government’s advice is more conservative than the CDC’s 2016 recommendation to use a product containing 20 to 50 percent DEET for adult protection against Lyme disease, and a product containing 20 to 30 percent DEET for children’s protection. Consumers must make their own decisions about which advice to follow when it comes to using DEET on children in areas with a high risk of Lyme disease.

Health Canada Recommendations for DEET Usage  

IR3535

IR3535, whose full chemical name is 3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester, is structurally similar to the naturally occurring amino acid B-alanine. Merck & Co. developed IR3535 in the mid-1970s. It has been used in Europe for more than 20 years, but was not registered for use in the U.S. until 1999.

IR3535 can be very irritating to the eyes, but poses few other safety risks. European authorities have received no reports of health problems caused by this chemical. Like DEET, IR3535 may dissolve or damage plastics. The manufacturer recommends avoiding contact with plastics other than polyethylene and polypropylene.

Merck recommends formulations with 10 to 30 percent IR3535 to repel biting insects and ticks.

A comprehensive review of public efficacy studies completed between 2000 and 2013 found the performance of IR3535 to be similar or slightly less effective than DEET and picaridin against mosquitoes. Against deer ticks, IR3535 provided over twice the mean protection time of DEET, picaridin or Oil of Lemon Eucalyptus.

This chemical is most often found in products sold as sunscreens and repellents. We recommend avoiding these products because sunscreen should be reapplied every two hours, but following those instructions would overexpose the user to bug repellent.

In sum, IR3535 is a good all-around option that should provide strong mosquito repellency and good tick repellency.

Oil of Lemon Eucalyptus/PMD

Oil of Lemon Eucalyptus is the trade name for the repellent that originated as an extract of the eucalyptus tree native to Australia. The tree extract is refined to intensify the concentration of the naturally occurring substance para-menthane-3,8-diol, also known as PMD, from 1 to 65 percent. The resulting oil is very different from unprocessed tree oil.

Most Oil of Lemon Eucalyptus products on the market are made by Spectrum Brands and sold under the brand names Repel and Cutter. These have concentrations of 30 percent Oil of Lemon Eucalyptus and 20 percent PMD. Some testing has shown that concentrations of 20 to 26 percent PMD may perform as well as 15 to 20 percent DEET against both mosquitoes and ticks. The Oil of Lemon Eucalyptus active ingredient by itself, PMD, has a maximum protection time against mosquitoes and ticks that is shorter than DEET’s, with only two hours of protection according to EPA documents. 

Refined Oil of Lemon Eucalyptus is classified as a biochemical pesticide, which the EPA defines as a naturally occurring ingredient that controls pests by nontoxic mechanisms. Ingredients in this category can qualify for EPA approval with less safety testing than synthetic chemical pesticides. These products must submit tests showing effectiveness. 

Because the dangers to children have not been thoroughly explored, products with Oil of Lemon Eucalyptus and PMD have labels that warn, "Do not use on children under the age of 3." The CDC also advises not to use on children under 3 years of age. Citronellol and other chemicals in the extract are known allergens.

Synthetic PMD can be found in some repellent products at a concentration of 10 percent. These products provide only a few hours of protection and also warn against use on children younger than 3 years old. They present less risk of allergic skin reaction than natural PMD.

Scientists do not know enough to determine differences between PMD and Oil of Lemon Eucalyptus, but one study found that Oil of Lemon Eucalyptus provided longer protection than the equivalent concentration of synthetic PMD.

We conclude that Oil of Lemon Eucalyptus has disadvantages and is not appropriate for all situations, but is a good choice for people who want a botanically based bug repellent.

2-Undecanone, or methyl nonyl ketone, is an EPA-registered repellent that also can be found naturally in many plants such as cloves, strawberries and tomatoes. It was first registered with the EPA for use as a dog and cat repellent, and has been patented as a repellent for use against apex predators such as wolves, bears and tigers. In laboratory studies, the ingredient showed no toxicity via oral and inhalation routes, but it demonstrated slight dermal toxicity and caused some dermal and eye irritations. There is only one product registered with the EPA to use 2-undecanone. It is sold as Bite Blocker BioUD and is registered to provide five hours of mosquito repellence and two hours of tick protection. There are very few public studies comparing the efficacy of 2-undecanone with other repellents, although it is effective as DEET is some tests.

West Nile virus struck more than 2,000 Americans last year. Two-thirds of those cases were complicated with a neuro-invasive disease such as meningitis, encephalitis or acute flaccid paralysis, according to the Centers for Disease Control and Prevention. Symptoms can include high fever, headache, stupor, tremors, convulsions and neurological damage. 

Between 1999 and 2008, 64 different mosquito species tested positive for West Nile virus.

According to the CDC, infections from mosquitoes carrying West Nile virus occur primarily in the summer months, peaking in August. West Nile cases have been found in almost every state in the nation, with the highest 2017 numbers reported in Arizona, Texas, California and Illinois.

Malaria can cause fever, chills, headache, vomiting, diarrhea and, in severe cases, organ failure, coma and death. In 2016, 91 countries and areas had ongoing malaria transmission, and nearly half of the world's population was at risk from malaria, according to the World Health Organization.

Some 30 to 40 of the 400 different species within the Anopheles genus transmit malaria. These species are widespread throughout the world.

What tests tell us – and what they don’t

Repellents are not tested against all mosquito species. The most common mosquito used in tests is the Aedes aegypti because it is very sensitive to repellents and easy to cultivate in laboratories. Other Aedes mosquito species require higher doses and more frequent reapplication of repellents.

One repellent may not always protect a person from all the different mosquito species, nor from other pests. 

Ticks

Diseases carried by ticks are rare, but can be severe. EWG recommends prudent tick prevention methods to anyone who spends time in tick-infested areas.

Eight tick species in the U.S. may carry disease.

Lyme disease, carried by the blacklegged tick and Western blacklegged tick, is the most prevalent tick-borne disease in the U.S., with 26,203 known and 10,226 probable cases reported in 2016, the latest year for which data are available.44 The actual numbers are likely much higher, according to a CDC analysis of clinician data, which provided an estimate of 329,000 cases annually.

Most cases occur from Virginia to Maine and in the upper Midwest – mostly Wisconsin and Minnesota.

Adult blacklegged ticks are about the size of a sesame seed. Most Lyme disease is transmitted via bites from immature nymphs that feed during the spring and summer. You are most likely to contract tick-borne Lyme disease between mid-April and August.

The lone star tick, found in the eastern half of the U.S., carries Southern tick-associated rash illness, an infectious disease similar to Lyme disease.

Rocky Mountain spotted fever can cause fever, headache, vomiting, muscle pain and, in some cases, death. It can be transmitted to humans by bites from the American dog tick, Rocky Mountain wood tick and brown dog tick. The disease has been reported throughout the lower 48 states, with most cases occurring in North Carolina, Oklahoma, Arkansas, Tennessee and Missouri. The incidence rate has increased over the past 20 years to more than 3,000 U.S. cases annually. But the fatality rate has greatly decreased over the past 50 years from 5 to 10 percent to less than 0.5 percent.

Protecting from ticks and Lyme Disease

Do repellents stop ticks?

No single chemical completely repels American ticks. Do not rely on any product to keep ticks away. Check for ticks at the end of the day or when returning indoors.

The Environmental Protection Agency has approved products using picaridin, IR3535, DEET and Oil of Lemon Eucalyptus/PMD for use as tick repellents with a protection time greater than two hours. In lab studies DEET only stops three of every four ticks, and products with lower concentrations were less effective. Researchers test tick repellents by timing how long it takes for a tick to walk over a volunteer’s repellent-coated skin. The effectiveness of tick repellents can vary according to species and lifecycle stage of the tick.

There are few peer-reviewed scientific studies of the efficacy of these chemicals against deer ticks. Two studies indicate that IR3535 repels deer ticks as well as or better than DEET. A 2013 science review of efficacy against deer ticks lists a mean protection time of 7.2 hours for IR3535, 3.5 hours for DEET, 2.7 hours for Oil of Lemon Eucalyptus/PMD and 2.5 hours for picaridin.

In one study, three repellents – 33 percent DEET, 20 percent picaridin and 20 percent IR3535 – repelled lone star ticks for some hours, but 10 percent IR3535 did not.

Does treated clothing keep ticks away?

According to the Centers of Disease Control and Prevention, clothing and gear treated with 0.5 percent permethrin, a registered pesticide, may be a good way to prevent tick bites.

Available efficacy testing indicates that permethrin-treated clothing provides a higher level of protection from ticks than repellents applied to the skin. However, permethrin is not without some concern. It is neurotoxic and the EPA has been classified it as a likely human carcinogen. It is highly toxic to the environment, especially to fish and other aquatic life. But a 2009 EPA review said that “permethrin factory-treated clothing is unlikely to pose any significant acute or chronic hazard to people,” including toddlers, pregnant women and nursing mothers.

Use permethrin products with caution, read labels, and wash all treated clothing separately from other clothing.