EWG’s 2018 Guide to Bug Repellents : Protecting from Zika Virus
What You Can Do About Zika
As of July, the Centers for Disease Control and Prevention have reported no cases of local transmissions of Zika virus in the continental United States in 2018.1 However, Zika remains a major concern in some U.S. territories and other parts of the world. Before traveling, check the CDC’s Areas with Risk of Zika map for the agency’s safety recommendations.
2016 estimated ranges of Zika-carrying Aedes mosquito species
Source: U.S. Centers for Disease Control and Prevention
“[Zika] is a very unusual virus that we can't even pretend to know everything about it that we need to know,”2 Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said at a White House briefing in 2016.
As the Zika virus is still prevalent in areas outside the continental U.S., EWG advises Americans – especially women who are pregnant or may become pregnant – to pay careful attention to the CDC’s Zika travel warnings, cover up and use bug repellents most likely to drive away Aedes species mosquitos. These mosquitos are suspected to be the primary carriers of the Zika virus, and they bite during the day and night.
However, beware of marketing claims that promise 100 percent protection. No bug repellent or chemical-infused clothing can credibly guarantee to fend off all mosquitos, but some repellents are better than others.
EWG scientists have grouped repellents in order of effectiveness:
- Picaridin (at 20 percent concentration)
- DEET (at 20 to 30 percent concentration)
In laboratory and field test conditions, these repellents offered the strongest protection from the Aedes mosquito. They should prevent or significantly reduce bites for at least four hours. It’s important to reapply your bug spray after swimming and sweating.
- IR3535 (at 20 percent concentration)
- Oil of Lemon Eucalyptus
The CDC recommends using products registered with the Environmental Protection Agency that contain any of the five active ingredients listed above. While EWG has tried to highlight the best bets for eliminating bug bites, we completely agree with the CDC’s recommendation that – regardless of which product you’re using – if you are still getting bitten, reapply or try a different product.
- Vitamin B1 patches
- Essential oils
Some essential oils may work for short periods of time, but others are ineffective against Aedes mosquitoes. Due to the serious risks Zika poses, EWG does not recommend blends of essential oils for people at risk of mosquito-borne infection.
If you’re pregnant
The clear and present danger of the Zika virus has irrevocably altered how pregnant women must think about insect repellents.
EWG and medical professionals have generally urged women to avoid exposure to chemicals during pregnancy. That conventional wisdom has been turned on its head by a virus that can inflict irreversible damage on the unborn child.
The CDC recommends, if possible, avoiding or postponing travel to areas where you may be at risk of contracting Zika.3 According to the World Health Organization, if you are someplace where you might contact Zika via an infected mosquito, take extra care to avoid mosquito bites throughout your pregnancy. The benefits of repellents outweigh any potential safety concerns they may pose.
A review by doctors at Harvard and Boston area hospitals reiterated that the added Zika protection from DEET- and permethrin-treated clothing outweighs any known risk from using these repellents.4
If you are pregnant and outside the known range of the Aedes mosquito, consult EWG’s repellent guide to learn about your risk from other mosquito-borne diseases.
Use synthetic repellents approved by the EPA and follow label instructions closely. Here are the details:
DEET is the only insect repellent that has been tested on pregnant women. These studies involved 897 women who applied DEET daily during their second and third trimesters. At 1 year old, the children of these mothers showed no birth defects, changes in body size or developmental problems.5
No studies have examined the children of women who applied DEET during the first trimester.
Many laboratory studies expose test animals to intense doses of chemicals to detect subtle or rare outcomes. The EPA approved DEET and other insect repellent chemicals after tests on pregnant animals in laboratory studies did not find any pregnancy-specific health risks, except at doses so high that they were toxic to the adult animals.
Always handle DEET with caution. It irritates the eyes and in intense doses may induce neurological damage. In very rare cases it has been reported to impair the nervous system, with symptoms including seizures, tremors and slurred speech, most often after exposure to high concentrations. Infants and children may be more sensitive to these rare neurological side effects.
Picaridin has not raised as many concerns about neurotoxicity as DEET, but it has also not undergone as much testing. EWG’s assessment is that it is a good alternative, with many of the same advantages and without the disadvantages of DEET.
The EPA says that picaridin has not induced developmental problems in the offspring of animals exposed to it – the chemical harmed young animals only when their mothers had been exposed to doses so high they were toxic.6
IR3535 is also a good DEET alternative, with many of the same advantages and fewer disadvantages than DEET. Products using IR3535 at a concentration of 20 percent performed much like DEET, but products with lower concentrations were not as effective.
In animal tests, IR3535 harmed young animals only when the mothers were exposed to toxic levels of the chemical. IR3535 has not been tested for effects on human pregnancies.
Oil of Lemon Eucalyptus and p-Menthane-3,8-diol (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 PMD from 1 to 65 percent. The resulting oil is very different from unprocessed tree oil.
Oil of Lemon Eucalyptus and PMD have not been thoroughly tested for their effects on children under 3 years old. EWG advises against using them on pregnant and nursing women, babies and toddlers. They are also less effective than other chemicals against Aedes mosquitoes that transmit the Zika virus.
Permethrin is sometimes embedded in textiles for mosquito control. Unlike other repellents, it acts on the insects’ nervous systems. Laboratory studies confirm that this chemical can also affect the human nervous system and impair a child’s developing brain. As with bug repellent lotions, you should assume that some amount of permethrin will rub off the clothing and penetrate the skin, but the EPA’s safety investigations have found that permethrin-treated clothing presents low risks to human health.
When infused into clothing, permethrin can deter mosquitos from landing and prevent bites by Aedes aegypti.7 The chemical’s effectiveness declines after washing. If you want to try it, buy clothing pre-treated at the factory. Don’t treat your own clothing with liquid permethrin.
Clothing and sun protection
Clothing made from tightly woven material should be one of the considerations for both sun and mosquito protection. If you need both sun and mosquito protection, the CDC recommends buying two separate products and applying sunscreen before mosquito repellent. Studies show that ingredients in sunscreen increase your skin’s capacity to absorb repellent.
1 Areas with Risk of Zika. Centers for Disease Control and Prevention, 2018. Available at www.cdc.gov/zika/geo/index.html
2 Daily Briefing. C-SPAN, April 11, 2016. Available at www.c-span.org/video/?407995-1/white-house-briefing
3 Zika Virus. Centers for Disease Control and Prevention, 2018. Available at www.cdc.gov/zika/index.html
4 Blair J. Wylie et al., Insect Repellents During Pregnancy in the Era of the Zika Virus. Obstetrics & Gynecology, 2016, 128(5):1111–1115. Available at www.ncbi.nlm.nih.gov/pmc/articles/PMC5737756/
5 R. McGready et al., Safety of the Insect Repellent N,N-diethyl-M-toluamide (DEET) in Pregnancy. American Journal of Tropical Medicine and Hygiene, 2001, 65:285-289. Available at www.ncbi.nlm.nih.gov/pubmed/11693870
6 New Pesticide Fact Sheet: Picaridin. Environmental Protection Agency, 2005. Available at www3.epa.gov/pesticides/chem_search/reg_actions/registration/fs_PC-070705_01-May-05.pdf
7 S. DeRaedt Banks et al., Permethrin-Treated Clothing as Protection Against the Dengue Vector, Aedes Aegypti: Extent and Duration of Protection. PLOS Neglected Tropical Diseases, 2015, 9(10)e0004109. Available at www.ncbi.nlm.nih.gov/pubmed/26440967