Five bug repellents scored high marks for preventing bites, and another did pretty well, but four common choices didn’t make the grade in May 2010 testing by Consumer Reports. As a parent and pediatrician, I want a mosquito and tick repellent that is safe, effective, and easy to use. It also helps if it doesn’t smell like bug spray.
Insect and arachnid bites aren’t just annoying; they are also the cause of hundreds of West Nile virus infections, about 1500 cases of malaria, and about 35,000 cases of Lyme disease diagnosed in the US each year – not to mention the million people who die from malaria each year around the world. Even though most mosquito bites are just an itchy nuisance and most tick bites are barely noticed, it’s important to have a reliable way to block bites when needed.
Repellent testing involves daring testers who put their bare arms in mosquito-filled cages and who let ticks crawl on them, while observes record how long it takes the critters to start biting. The top five products prevented bites from ticks and two important species of mosquitoes for at least the full eight hours of the test. In four of these winners, the active ingredient was DEET. The other was a plant-based repellent using oil of lemon eucalyptus:
- Off Deep Woods Sportsmen II (DEET 30%)
- Cutter Backwoods Unscented (DEET 23%)
- Off FamilyCare Smooth and Dry (DEET 15%)
- 3M Ultrathon Insect Repellant 8 (DEET 25%)
- Repel (Plant Based Lemon Eucalyptus)
Another repellant scored almost as well, but the volunteers did start getting mosquito bites after 7 hours:
- Natrapel 8-Hour with Picardin (Picaridin)
All of the above repellents use active ingredients registered with the EPA and included in the CDC recommendations for preventing diseases spread by insect bites.
Other products tested had some benefit, but scored much lower overall:
- Avon Skin-So-Soft Bug Guard Plus IR3535 Expedition SPF 30 (IR3535)
- Bite Blocker Xtreme (Plant Oils)
- Cutter Skinsations Clean Fresh Scent (DEET 7%)
- Burt’s Bees All Natural Herbal (Plant Oils)
How safe are the top repellents?
The EPA rates DEET as Category III (slightly toxic) for acute oral or dermal exposures. DEET is irritating to the eyes and mucus membranes. Skin rashes are the most common side effect and are uncommon. Suspected serious adverse reactions are rare, but include seizures and encephalopathy in children. DEET is considered slightly toxic to birds, fish, and aquatic invertebrates. The EPA says that child safety claims on some DEET products are misleading and not allowed because concentrations lower than 30% are not known to be any safer. Because the risks are well understood, DEET is recommended by the CDC and AAP for use on babies down to 2 months old, but is not considered safe for newborns.
Likewise, the EPA considers picaridin Category III (slightly toxic) for acute oral or dermal exposures. In animal studies it caused slight to minimal liver hypertrophy, individual necrotic liver cells, chronic kidney inflammation, and slight kidney degeneration when ongoing large amounts of picaridin were applied to the skin. They found no evidence that it is an endocrine disruptor or carcinogen. It is nontoxic to birds and moderately toxic to fish.
I prefer the plant-based oil of lemon eucalyptus. No adverse effects have been found, other than eye irritation. The EPA considers it Category IV (practically non-toxic), for acute oral or dermal exposures – indeed for any route except being splashed in the eyes (so use lotion or use spray in the palm to apply to face). They’ve determined that it poses minimal or no risk to wildlife and is not harmful to the environment. The EPA assessment concludes that it is not expected to pose health risks to people, including children, pregnant women, or other sensitive populations. Nevertheless, the official recommendation is not to use it on children younger than 3 because testing has not yet been done on young children.