What’s the Safest Mosquito Repellent?

#EcoAdvice from our expert

Dear Dr. Donley,

I live in Texas, where locally transmitted cases of the Zika virus have been confirmed, and my toddler’s preschool requires that we provide her with bug spray. What is the safest and most effective bug repellent for my family?

Signed,

I’m So Zika These Mosquitoes!

Dear Stressin’ Texan,

Our climate is changing, and like it or not, we now live in a country where Zika is going to be a threat in certain regions. Other mosquito-borne diseases, such as Dengue fever and West Nile virus, may also be on the upswing. Instead of panicking and spraying pesticides from airplanes over our homes, schools and playgrounds — which has questionable effectiveness against the Aedes albopictus and Aedes aegypti (Zika-carrying) mosquitoes and can do more harm than good — we should act personally to make sure we’re protected from mosquito-borne diseases.

You asked about bug spray, and I promise I’ll get to that soon. But more important than what bug repellent you choose is the common-sense, practical action you can take to reduce your exposure to mosquitoes. Removing the standing water where mosquitoes breed from homes, yards, public spaces and schools is critical. Any water that has collected in playground equipment, discarded toys and tires or clogged gutters can serve as a breeding ground. Zika-carrying mosquitoes generally don’t travel far from where they hatch, so your first line of defense should always be reducing the number of suitable places where those pesky buggers can breed.

Second, reduce exposure by making sure that all windows have properly functioning screens. Promptly fix screens that have holes in them. And a lot of bug bites can be prevented by wearing long pants, long shirts and hats when going outside in the land of mosquitoes.

These steps are immensely important for reducing potential exposure to disease-carrying mosquitoes and should never be underestimated.

In addition to these steps, mosquito repellant may also be warranted. The first consideration should always be: Does it work? Once you’ve identified the ingredients that work, then you can begin to make the decision on which are the safest. There are seven ingredients that have been approved by the CDC and EPA for use in repelling mosquitoes and have been proven to be effective, four of which are widely available:

1) DEET

2) Picaridin

3) IR3535

4) Oil of Lemon Eucalyptus / PMD

Although DEET is very effective, there are other alternatives that are just as good. DEET has been correlated with neurotoxicity at high concentrations and is a common pollutant found in nearly three quarters of streams tested in the United States — almost all thought to come from people showering after applying it to their skin. If you do use DEET, do not use greater than 10 percent on children under 12 and 30 percent on adults. Higher concentrations do not increase effectiveness and just lead to unnecessary exposure.

Picaridin is probably going to be your best bet. Ingredients with 20 percent picaridin were found to be just as effective and long-lasting as DEET at repelling Zika-carrying mosquitoes. Picaridin also does not have the same neurotoxicity concerns as DEET, although it has undergone less scrutiny.

IR3535 is slightly less effective than Picaridin or DEET, but still more than adequate to repel mosquitoes. IR3535 and DEET can dissolve some plastics, which is not necessarily an indication that they are harmful but nevertheless a bit unsettling.

Those seeking a more natural alternative may be drawn to lemon eucalyptus oil, though this product has generally been refined to increase the concentration of the active ingredient, PMD, to very high levels. Still, it’s a very effective repellent against Zika and other mosquitoes (though not recommended to repel certain mosquitoes that may carry West Nile virus). Since it’s a natural ingredient, less safety testing has been required, and because of this lemon eucalyptus oil is not recommended for use on children under three years of age.

Whatever ingredient you choose, it’s important to only use the least amount needed to repel mosquitoes. Avoid aerosol sprays — they can easily be unintentionally inhaled. Pump-action sprays or lotions are more easily controlled. Spray or rub the product on your hand first, then apply to your child. Avoid the eyes and mouth, and don’t apply it to their hands (because those hands will end up in their mouth at some point). You don’t need to load it on — a thin layer is all it takes. And don’t forget to wash your hands when you’re done.

When you’re shopping for a repellent, just check out the ingredient list on the back of the product to see what it contains. For more in-depth information, I recommend a report by the Environmental Working Group.

Stay wild,

Dr. Donley

Dr. Nathan Donley is a scientist at the Center for Biological Diversity who answers questions about how environmental toxins affect people, wildlife and the environment. Send him your questions at AskDrDonley@biologicaldiversity.org

Read the previous Ask Dr. Donley installment What are the Safest Flea Treatments for Pets?”