LOS ANGELES, CA (Catholic Online) - Scientists from the London School of Hygiene and Tropical Medicine found mosquitoes have grown accustomed to the smell. It must be noted that DEET doesn't kill mosquitoes, but works as a deterrent. According to a recent study, the mosquitoes were initially repelled by the chemical, but ignored it just a couple hours later.

"What we found was the mosquitoes were no longer as sensitive to the chemical, so they weren't picking it up as well," Dr. James Logan told the BBC.

"There is something about being exposed to the chemical that first time that changes their olfactory system - changes their sense of smell - and their ability to smell DEET, which makes it less effective."

Originally developed by the U.S. military for use in jungle warfare, DEET was approved for use by the general public in 1957. DEET appears in a variety of sprays, lotions and other insect repellant products.

The Centers for Disease Control names DEET, along with picaridin and oil of lemon eucalyptus, as the most effective ingredients against the mosquito-borne West Nile virus and is also effective against disease-carrying ticks that carry lyme disease.

Consumer worries have persisted over the use of DEET for many years. Some research has found that heavy exposure can cause memory loss, headache, muscle and joint pain, and fatigue.

The Environmental Protection Agency ruled in 1998 that DEET does not pose a health concern to humans as long as exposure is brief and consumers follow label directions. The American Academy of Pediatrics recommends that products containing DEET not be used on infants younger than two months of age.

Another disease that mosquitoes carry is malaria, which has since a noticeable uptick in Southeast Asia and Africa. Many children have fallen ill and died in these parts of the world, and there is widespread concern that malaria may spread into more densely populated areas.

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