How Insect Repellent Works

Insect Repellents

Insect repellents generally fall into two categories, those based on synthetic chemicals such as DEET, and natural botanically-derived formulations such as Deter.  Science is beginning to understand the biting behavior of insects, and what attracts/repells them.  Most insect repellents work at the molecular level by triggering an avoidance response initiated by chemical receptors on the insect analogous to taste and smell.  The receptors are located on the insects tongue and appendages. Some receptors react to a sense of “smell” creating the avoidance response when the insect first detects the repellent. Other receptors act like a ���taste” sense so that even if the insect lands it will not bite once it detects the repellent.  The most effective repellents work by triggering both the “smell” and “taste” receptors.  Deter is specifically formulated to not only trigger the “smell” and “taste” receptors, but also work on a wide range of insect species.  Using a repellent such as Deter that has a broad spectrum of activity can greatly increase effectiveness.  Most repellents are volatile (readily evaporate), an important aspect of how they work.  Therfore, they must be applied frequently to all exposed skin in order to maintain maximum effectiveness.  Environmental factors must be taken into consideration when deciding how often to apply.  These factors include temperature, humidity, insect activity, sweating, etc. Generally speaking more frequent application should be considered in hot humid weather, when sweating excessively or when insect activity is high.  Application frequency can range from about an hour to over 4 hours depending on conditions and the product being used.  Insect repellents should always be applied according to label directions.


Why DEET Free?

DEET is short for N,N-diethyl-meta-toluamide a chemical developed by the U.S. army in 1946 to help protect soldiers operating within insect infested areas.  DEET is an effective insect repellent that has been used by millions of people for over 6 decades. However, it does have a number of undesirable attributes including its unpleasant odor and ability to severely damage many plastic products (i.e., sunglasses and other personal plastic items).  Additionally, there is a growing body of data that suggests DEET may pose health risks.  DEET is absorbed when applied to the skin.  Studies show that up to 56% of DEET is absorbed by intact skin and 17% is absorbed into the blood stream.  Studies suggest that DEET may have toxic effects on the central nervous system.  Studies at Duke University showed that lab animals exposed to doses of DEET equivalent to those recommended for human use resulted in significant impairment of neuro-behavioral tasks requiring muscle coordination. Other studies suggest exposure to DEET can lead to motor deficits, learning and memory dysfunction.  These findings are consistent with reported human toxicity that includes seizures and serious gastrointestinal symptoms.  Due to safety concerns Health Canada has banned products with DEET concentrations over 30%.