Published on July 1st, 20130
Don’t Get Bugged Out by Insect Repellent Claims
DEET is the most common ingredient in insect repellents. It is found in products in concentrations up to 100%. The percentage of DEET does not determine how effective it will be, but rather for how long it will be effective. The higher the percentage of DEET in a repellent, the longer it offers protection. Concentrations of 100% are supposed to last around 12 hours, but a study from The New England Journal of Medicine says that real-life effectiveness actually plateaus around 50%. Concentrations under 10%, on the other hand, have limited effectiveness.
The advantage to DEET is its long track record of being effective and safe, as long as it’s used according to the label. Despite all the testing, however, many consumers still worry about DEET’s safety. Some people who have been exposed to very high doses of DEET, such as those in the military, have experienced severe skin reactions, insomnia, and mood changes. The American Academy of Pediatrics recommends that repellants should contain no more than 30% DEET when used on children; a great guide from Consumer Reports recommends the same for adults, along with suggestions for specific products.
Picaridin (or Icaridin) is a newer insect repellent ingredient that is less irritating to the skin than DEET. It is a synthetic version of piperine, which is found in black pepper. Picaridin has been available for years in Europe, but it was only approved in the U.S. in 2005. In order to be as effective as DEET, picaridin must be used in slightly higher concentrations. A product that is 7% picaridin is about as effective as a 10% DEET solution. For better results, consumers may want to look for products with a concentration of around 20%, which should be effective for 4-5 hours of protection.
Oil of Lemon Eucalyptus or PMD
PMD is a synthetic version of oil of lemon eucalyptus (OLE) used in insect repellents. On labels, PMD and OLE are used interchangeably, but actually “pure,” unrefined OLE is a distinct chemical, and it is not as effective a repellent. Studies have found that concentrations of between 20%-50% PMD can provide two to twelve hours of protection against certain mosquito species. The CDC includes OLE (as well as DEET, and picaridin) on its list of repellents that typically provide reasonably long-lasting protection.
Common natural (meaning plant-based) alternatives to DEET include citronella, soybean oil, and various essential oil blends. Some people choose to avoid synthetic repellents due to safety or environmental concerns, but according to a review published in Malaria Journal, natural insect repellents are not necessarily any safer or better for the environment. DEET has been rigorously tested for many years, but repellents with natural ingredients have not been studied as closely. Some natural extracts used in insect repellents, like anise, basil, or cajeput, may even be harmful. As for effectiveness, more research might be necessary, but for now it seems that plant-based repellents do not compare well with other options.
Repellents with Sunscreen
The CDC recommends against using combination repellent/sunscreen products. The sunscreen can be less effective when combined with repellent. Also, sunscreens are meant to be applied liberally and repeatedly, whereas insect repellant is meant to be applied more sparingly. Using a combination product for optimal sunscreen effectiveness could result in the over-application of repellant.