Since World War II, Deet has been recommended as a deterrent against mosquitoes. When initially introduced to mosquitoes, Deet’s odor is the primary deterrent; however, it doesn’t affect all mosquitoes equally. After several exposures to Deet, most mosquitoes do not react as quickly. Is this a result of evolutionary adaptation or habituation? Either way, Deet is still the most common active ingredient in insect repellents today.
Why is it losing its effectiveness?
Mosquitoes, like most living things, evolve quickly to their environment. Unfortunately, the chemical Deet has been very widely used and mosquitoes and other insects are becoming increasing immune. Due to its extended use without alterations, some may say Deet is becoming outdated.
One probable cause is evolutionary adaptation. Basically, the short breeding cycle and continuous exposure to Deet have aided in developing Deet immune mosquitoes. The mosquitoes have genetically altered themselves through “survival of the fittest” by mutating the protein that binds Deet to the mosquitoes’ antennae.
Another equally probably cause is habituation. Habituation is simply the result of mosquitoes being exposed to Deet many times and becoming less sensitive. Habituation is a behavioral adaptation, which isn’t passed down genetically.
What does this mean for me?
The current recommendation is to reduce large scale, habitual sprayings of Deet so to prevent more Deet immune mosquitoes from breeding. However, researchers do not believe that we should stop using Deet entirely.
First, Deet is used to prevent many diseases such as malaria and dengue. A benefit-risk analysis would recommend using the Deet, however effective it may be, rather than risk contracting malaria or dengue.
Next, mosquitoes have a short breeding cycle but they also only live as adults but for a few days. There is controversy as to whether or not the evolutionary adaptation is actually genetically passed down to offspring or if it is indeed habituation. If the latter is correct, it isn’t likely that the specific mosquito hovering over your arm has already been exposed to Deet.
Are there any alternatives?
Yes! The Center for Disease Control (CDC) recommends two Deet alternatives: Picaridin and Oil of Lemon Eucalyptus. The first, Picaridin, is typically found in Europe, Australia, Asia, and Southern America but is now available in the US. The second, Oil of Lemon Eucalyptus, is a plant-based insect repellent that comes from eucalyptus leaves. It too, is found in the US. Deet, Picaridin, and Oil of Lemon Eucalyptus all work the same way in that they create a barrier between the skin and the mosquito.