Is insect repellent bad for your skin?

If you've spent much time outdoors, chances are you've had to fight with mosquitoes intent on making you a meal. Mosquitoes are more than just a nuisance. They transmit diseases like encephalitis, malaria and West Nile virus to hundreds of millions of people every year [source: CDC]. Add in the threat of catching Lyme disease from ticks, and it's easy to understand the importance of insect repellent.

Different insect repellents contain different active ingredients, some natural and some artificial, but all of them work in a similar way. Insects, particularly mosquitoes, are drawn to the carbon dioxide people release when they breathe, as well as certain odors from the skin. Insect repellent has the same effect on insects as bad cologne or perfume does on people -- avoidance. Interestingly enough, insect repellent doesn't actually harm insects, making it fundamentally different from pesticides.

So repellents don't harm insects, but can they harm you? For the most part, the answer is "no." The most popular repellents are registered with the U.S. Environmental Protection Agency (EPA), which tests their safety and effectiveness. The list of registered repellents is a short one, including the synthetic repellent DEET, as well as the natural repellents picaridin and oil of lemon eucalyptus, though you can find other repellents like citronella and IR3535 on the shelves.

While some of these repellents have undergone more testing than others, they all prove safe for the vast majority of people when used according to their safety guidelines. Yet insect repellents, by their very nature, work by spending hours in contact with the skin. Can these chemicals that insects abhor possibly be OK for your skin? Read on to find out.

The Buzz on Insect Repellents and Their Effects

If something as seemingly benign as sunlight can harm your skin, it's not hard to imagine that insect repellents might do the same. In fact, insect repellents can cause skin rashes and irritation. For instance, one study found nearly half of the people using a highly concentrated formula of DEET on the sensitive inner elbow reported adverse effects [source: ASTDR]. The good news is that if one repellent reacts badly with your skin, you probably can find another one that doesn't. Let's look at some of the most popular insect repellents to learn what they're made of and how they affect your skin.

DEET

By far the most popular repellent sold in the United States, DEET was used by more than 200 million people worldwide in 2008 [source: ASTDR]. It's perhaps the most effective repellent on the market, particularly when used in high concentrations. Unfortunately, frequent use of repellents containing a high percentage of DEET can cause a number of adverse reactions, including blisters, rashes and even scarring. Even so, negative reactions to DEET are rare considering the number of people who use the repellent, and washing your skin after returning indoors can help further reduce irritation from exposure.

IR3535

IR3535 is a synthetic repellent available in concentrations of up to 20 percent. The repellent has proven to be nontoxic, causing no skin irritation to speak of. While IR3535 has a great safety record, its effectiveness can't match DEET's. According to one study, IR3535 was found to be only one-eighth to one-hundredth as effective as a similarly concentrated DEET repellent [source: Fradin].

Picaridin

Derived from pepper, picaridin is widely available in Europe and Australia, but is only available in lower concentrations in the United States, barring further study. The repellent appears to be completely safe for the skin, though it can still cause irritation if it touches the eyes. Best of all, one study found picaridin to last 70 percent as long as DEET, making it a highly effective alternative [source: MSDH].

Oil of lemon eucalyptus

Derived from a particular species of eucalyptus tree, oil of lemon eucalyptus is one of only three repellents registered with the U.S. Environmental Protection Agency. Research has shown oil of lemon eucalyptus, often referred to as PMD, to be the most effective of all plant-based repellents. Studies have shown PMD to cause eye irritation but little else, though individuals have reported occasional skin irritation after using a PMD-based repellent.

Overall, insect repellents are safe and effective, providing more good than harm for users. By following the instructions provided on repellents' labels, you put yourself and your skin at very little risk using any insect repellents currently on the market.

Repellents Three Times as Good?

Researchers from the University of Florida recently set out to find an insect repellent even more effective than the ones currently on the market. After isolating 34 of the most promising formulations, the researchers found some bold participants to test the repellents in mosquito-filled cages. Their research paid off; several of the repellents fended off mosquito bites three times longer than DEET, the current champ in bite protection [source: Highfield].

Lots More Information

Sources

ASTDR. "DEET - Health Effects in Humans." Dec. 6, 2004. (10/2/2009)http://www.atsdr.cdc.gov/consultations/deet/health-effects.html
Centers for Disease Control and Prevention. "Insect Repellent Use and Safety." May 14, 2008. (10/2/2009)http://www.cdc.gov/ncidod/dvbid/westnile/qa/insect_repellent.htm
Centers for Disease Control and Prevention. "Malaria Facts." April 11, 2007. (10/2/2009)http://www.cdc.gov/Malaria/facts.htm
EXTOXNET. "Pesticide Information Profile: Deet." Oct., 1997. (10/2/2009)http://pmep.cce.cornell.edu/profiles/extoxnet/carbaryl-dicrotophos/deet-ext.html
Fradin, Mark S. "Insect Repellents." eMedicine. May 5, 2009. (10/2/2009)http://emedicine.medscape.com/article/1088411-overview
Frost, Alexandra C. "Oil of Lemon Eucalyptus as an Insect Repellent." AHC Media. August, 2005. (10/2/2009)http://www.ahcpub.com/hot_topics/?htid=1&httid=1342
Highfield, Roger. "New insect repellent lasts three times longer." Telegraph.May 30, 2008. (10/2/2009)http://www.telegraph.co.uk/science/science-news/3343205/New-insect-repellent-last-three-times-longer.html
Mississippi Department of Health. "Mosquito Repellents." June, 2006. (10/2/2009)http://www.msdh.ms.gov/msdhsite/_static/resources/1683.pdf
National Pesticide Information Center. "Picaridin Technical Fact Sheet." March, 2009. (10/2/2009).http://npic.orst.edu/factsheets/Picaridintech.pdf
New York State Department of Health. "Health Advisory: Tick and Insect Repellents." April, 2009. (10/2/2009)http://www.health.state.ny.us/publications/2737/
U.S. Environmental Protection Agency. "3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester (113509)." February 1999. (10/2/2009)http://www.epa.gov/opp00001/biopesticides/ingredients/tech_docs/tech_113509.htm
U.S. Environmental Protection Agency. "Active Ingredients found in Insect Repellents." July 5, 2007. (10/2/2009)http://www.epa.gov/opp00001/health/mosquitoes/ai_insectrp.htm
U.S. Environmental Protection Agency. "The Insect Repellent DEET." March 23, 2007. (10/2/2009)http://www.epa.gov/pesticides/factsheets/chemicals/deet.htm

Is Insect Repellent Bad for Your Skin?